The main purpose of patent priority is to give the same applicant a security period for filing a patent application on the same subject in different countries, excluding the possibility for plagiarists to file a preemptive application and obtain a patent. 

I. Relating regulations in the Chinese Patent Law and Implementing Regulations of The Patent Law

Article 29. Where, within twelve months from the date on which any applicant first filed in a foreign country an application for a patent for invention or utility model, or within six months from the date on which any applicant first filed in a foreign country an application for a patent for design, he or it files in China an application for a patent for the same subject matter, he or it may, in accordance with any agreement concluded between the said foreign country and China, or in accordance with any international treaty to which both countries are party, or on the basis of the principle of mutual recognition of the right of priority, enjoy a right of priority. (Foreign Priority)

Where, within twelve months from the date on which any applicant first filed in China an application for a patent for invention or utility model, or within six months from the date on which any applicant first filed in China an application for a patent for design, he or it files with the patent administration department under the State Council an application for a patent for the same subject matter, he or it may enjoy a right of priority. (Domestic Priority)

Rule 32 (draft). An applicant may claim one or more priorities for an application for a patent; where multiple priorities are claimed, the priority period for the application shall be calculated from the earliest priority date.

Where an applicant claims the right of domestic priority, if the earlier application is one for a patent for invention, he or it may file an application for a patent for invention or utility model for the same subject matter; if the earlier application is one for a patent for utility model, he or it may file an application for a patent for utility model or invention for the same subject matter. Where an applicant claims the right of domestic priority, if the earlier application is one for a patent for invention or utility model, he or it may file an application for a patent for design for the same subject matter shown in the drawings; if the earlier application is one for a patent for design, he or it may file an application for a patent for design for the same subject matter; However, when the later application is filed, if the subject matter of the earlier application falls under any of the following, it may not be taken as the basis for claiming domestic priority:

(1)  where the applicant has claimed foreign or domestic priority;

(2)  where it has been granted a patent right;

(3)    where it is the subject matter of a divisional application filed as prescribed.

Where the domestic priority is claimed, the earlier application shall be deemed to be withdrawn from the date on which the later application is filed, except for situations where an applicant of the design patent application claims the right of domestic priority, and the earlier application is one for a patent for invention or utility model.

II. Claiming the priority of the first filed application

The time limit for claiming priority for Chinese invention and utility model patent applications is within twelve months from the earliest priority date, and the time limit for claiming priority for Chinese design patents is within six months from the earliest priority date. However, according to Rule 32 of the Provisions, the subject of an earlier application " where the applicant has claimed foreign or domestic priority" cannot be serve as the domestic priority basis. That is to say, the priority basis should be the application in which the technical means first appeared. For example, if an applicant filed a Chinese application A first, and then filed a Chinese application B with the same specification, and after that, the applicant wants to file an application C, if the technical means described in both the application A and application B, then application C should claim the priority of application A as a priority basis instead of application B. However, if new contents are added to application B, and the application C includes the newly added contents of application B, then we usually need to claim priorities of both the application A and application B when filing.

Further, about the first filed application, according to Paris Convention, Article 4, Part E:

A subsequent application concerning the same subject as a previous first application within the meaning of paragraph (2), above, filed in the same country of the Union shall be considered as the first application, of which the filing date shall be the starting point of the period of priority, if, at the time of filing the subsequent application, the said previous application has been withdrawn, abandoned, or refused, without having been laid open to public inspection and without leaving any rights outstanding, and if it has not yet served as a basis for claiming a right of priority. The previous application may not thereafter serve as a basis for claiming a right of priority.

In other words, if there is a later application that meets the mentioned application conditions in Article 4, Part E, the later application can be "upgraded" to the first application, which can be used as the basis for priority, and its filing date will become the starting date of the priority period. The original first application can no longer be served as the basis for claiming priority.

III. Claiming priority of a different type of patent application

As can be seen from Rule 32, for domestic priority, 1) a Chinese invention patent application can claim the priority of an earlier Chinese invention patent application or a Chinese utility model patent priority, 2) a Chinese utility model application can claim the priority of an earlier Chinese invention patent application or a Chinese utility model patent application, 3) A Chinese design patent application can claim the priority of a Chinese invention patent application, a Chinese utility model patent application or a Chinese design patent application.

Regarding foreign priority, the Regulations do not give specific provisions, but in accordance with the Paris Convention, Article 4, Part E:

(1) Where an industrial design is filed in a country by virtue of a right of priority based on the filing of a utility model, the period of priority shall be the same as that fixed for industrial designs.

(2) Furthermore, it is permissible to file a utility model in a country by virtue of a right of priority based on the filing of a patent application, and vice versa.

It can be seen that for foreign priority, 1) a Chinese invention application can claim the priority of an earlier foreign invention patent application or a foreign utility model patent application, 2) a Chinese utility model application can claim the priority of an earlier foreign invention patent application or a foreign utility model patent application, 3) a Chinese design patent application can claim the priority of an earlier foreign utility model patent application or a foreign design patent application. Although the above Article does not stipulate whether a Chinese design patent application can claim the priority of an earlier foreign invention patent, according to Chinese application practice, Chinese design patent application can claim priority of a foreign invention patent application (according to our search result, many Chinese design patent applications that claim priority for foreign invention patents were granted).

Where a design application claims the priority of an invention or a utility model patent application, the time limit is six months from the earliest priority date rather than twelve months.