Abstract: The core unit of subsea production system is the subsea control module (SCM). The realization of the control function of the SCM mainly relies on the hydraulic power to provide the driving force for the subsea tree valves. According to relevant statistics, 80% of hydraulic component failures are related to the deterioration of hydraulic oil. The largest proportions of deterioration and the most likely to occur are hydraulic oils containing mechanical impurities that result in unsatisfactory cleanliness. Therefore, the flushing of the hydraulic system is an important task before the subsea control system is used. The authors of this article proposed a complete SCM hydraulic flushing process and testing standard from the perspective of the SCM hydraulic system designer and producer. The basic parameters of the required equipment were listed in detail, providing a reference for the SCM flushing work.