In this paper, the annual maintenance and pre-test work of converter station is completed by adopting the outage method of double-pole simultaneous stop, and the content and organization of maintenance and pre-test are planned to form a scientific and reasonable annual maintenance method of converter station. Taking converter transformer and other DC equipments as the research object, focusing on exploring the DC resistance, partial discharge and other preventive test methods of DC equipments. Through the construction of simulation model or field test, this paper completes the DC resistance and partial discharge test of converter transformer and DC equipment winding. The simulation and field test results fully illustrate the effectiveness of the DC equipment preventive test methods proposed in this paper.