This paper takes the case of Xintai Electric's IPO lawyer and law firm against China Securities Regulatory Commission as a sample to analyze the identification standard of securities lawyers' diligence and responsibility obligations. From 1993 to 2019, China's securities laws were constantly improved, related securities regulatory agencies were also constantly improved and developed, and the administrative penalties made by them also showed an increasingly judicatory trend. Therefore, the determination of the standards of the obligations of the securities lawyers is becoming more and more clear and clear. But there are still many problems in practice. This paper mainly focuses on the determination of the judgment standard of the securities lawyers' diligence and duty, summarizes the causes and development of the case of Xintai Electric IPO lawyers and law firms against the CSRC, makes horizontal comparison of similar cases, vertically examines the evolution of legislation and judgment at home and abroad, and puts forward several opinions on the improvement of relevant laws in China.