Double-certificate lawyer, also known as patent double-certificate agent, usually refers to a lawyer who has both a lawyer's certificate and a patent agent's certificate. Dual-certificate lawyers can not only represent patent applications, but also conduct patent litigation, and are the main force in dealing with patent reexamination, invalidation and infringement. The concept of "double-certificate lawyer" refers to employees who have both lawyer's practice certificate and patent agent's practice certificate. "Double-certificate law firm" generally refers to the legal service institution that obtains the patent agency registration certificate while obtaining the practice license of the law firm. Law firms in China can apply for patent agency business, but they cannot run accounting, finance and other peripheral businesses concurrently. Therefore, due to the restriction of full-time lawyers' practice, lawyers with notes and financial qualifications cannot have practice certificates in the above fields at the same time, so they cannot become real dual-certificate lawyers.