How long does it take for the substantive examination of the invention patent?

Legal analysis: The time of patent substantive examination is uncertain, usually six to eighteen months. The time for examining the substance of a patent depends on the content of the invention, the examiner's understanding of the invention, the examiner's work arrangement and the time for the documents to and from the applicant or his agent.

Legal basis: Article 35 of the Patent Law of People's Republic of China (PRC). Within three years from the date of filing, the administrative department for patent in the State Council may, upon the request of the applicant at any time, make a substantive examination of the application. If the applicant fails to request substantive examination within the time limit without justifiable reasons, the application shall be deemed to have been withdrawn.