According to the detailed rules for the implementation of China's patent law, after accepting the request for invalidation of a patent, the patent administration department will send the request for invalidation of a patent and relevant evidence to the patentee for the patentee to state his opinions. Relevant laws stipulate Article 68 of the Detailed Rules for the Implementation of the Patent Law of People's Republic of China (PRC). The Patent Reexamination Board shall send a copy of the request for invalidation of the patent right and relevant documents to the patentee, asking him to state his opinions within a specified time limit. The patentee and the claimant for invalidation shall reply to the notice of transferring documents or the notice of examining the request for invalidation issued by the Patent Reexamination Board within a specified time limit; Failure to reply within the time limit shall not affect the trial of the Patent Reexamination Board. Article 69 In the process of examining the request for invalidation, the patentee of a patent for invention or utility model may amend his claim, but shall not expand the scope of protection of the original patent. The patentee of a patent for invention or utility model shall not modify the patent specification and drawings, and the patentee of a patent for design shall not modify the pictures, photographs and brief descriptions. Patent Invalidation Defense Fee (1) Self-defense At present, enterprises do not need to pay any official fees to defend their invention patents invalid. Because the patent invalidation defense is not initiated by the enterprise, but is passively triggered by the Patent Reexamination Board after accepting the request for invalidation of the invention patent put forward by others, asking the enterprise to submit statements and relevant evidence materials within the prescribed time limit, so the enterprise only needs to actively respond to the lawsuit to complete the defense without paying official expenses. (2) The sued enterprise may entrust a patent agency to defend the invalid invention patent. At present, the service fee for defending invalid invention patents in the industry is generally 10000-20000 yuan, which varies according to the popularity, influence and service quality of patent agencies. In the defense procedure of invalid patentee, it is necessary to distinguish whether to defend himself or entrust a lawyer. There are also requirements for the time limit for defense, and the defense cannot be continued beyond the time limit. When the patent is invalid, if the party concerned fails to make any reply, it will not continue to affect the final decision of the hearing.