legal ground
Article 34 of the Patent Law of People's Republic of China (PRC)
After receiving an application for a patent for invention, the administrative department for patent in the State Council, after preliminary examination, finds that it conforms to the provisions of this Law, and shall publish it immediately after 18 months from the date of application. The patent administration department of the State Council may publish its application at an early date upon the request of the applicant.
Article 35
Within three years from the date of filing, the patent administration department of the State Council may conduct substantive examination according to the request made by the applicant at any time; If the applicant fails to request substantive examination within the time limit without justifiable reasons, the application shall be deemed to have been withdrawn. The patent administrative department of the State Council may, when it deems it necessary, examine the application for a patent for invention on its own.