You need to check whether your patent is an invention or a utility model.
According to the Implementing Rules of the Patent Law, applicants for invention patents are only allowed to submit a request for substantive examination and after receiving the request from the Patent Office. Within 3 months from the date of issuance of the notification that the invention patent application has entered the substantive examination stage, the applicant shall proactively propose modifications to the invention patent application documents. If the applicant makes modifications to the patent application documents after receiving the notice of examination opinion issued by the Patent Office, the modifications shall be made in accordance with the requirements of the notice.
Applicants for utility model and design patent patents are only allowed to proactively propose modifications to utility model or design patent applications within 2 months from the filing date.