Abstract: The hydraulic drive system is the most important part of the mechanical system and has been widely used in various industries. It has strong adaptability and can achieve a good control eff ect without investing too much operating cost. However, during the actual operation of the sub-ah, under the infl uence of various factors, frequent failures will occur, resulting in the failure of the entire system to maintain normal operation. This article focuses on the hydraulic transmission system from the aspect of operation principle, and studies the common failures of the system and its countermeasures. Finally, the corresponding repair and maintenance strategies are put forward for diff erent failures. The purpose is to promote the good function of the hydraulic transmission system. Play, so that the mechanical hydraulic transmission system can have a longer service life.