Abstract: With the application and development of flexible high voltage direct current power transmission technology, the higher requirement for the reliability testing of valves in voltage source converter based high voltage direct current(VSC-HVDC) is continually put forward, it leads to existing testing system unable to simultaneously satisfy such requirements of valve control system as the full-scale accessing, full-functional testing and accurate modeling of valve base control system. In allusion to the inadequacy of existing testing system, firstly, based on RTLAB platform an accurate modeling was performed. Secondly, the interface devices with high performance, which could be flexibly configurated, were designed and a full access testing system for valve base control system was constructed. Thirdly, the key test items and testing method for the valve base control system were proposed. The designed test system and its testing methods have been applied to the ex-factory test of valve base control system in Beijing converter station of Zhangbei flexible HVDC power transmission project. The valve base control system that successfully passed the testing operates stably and reliable in engineering field.