Because of longer operating time and performance defects, HVDC control and protection system of Longquan converter station malfunctioned frequently in recent years, then it has adverse effect on power grid operating security. The faults that occurred in recent years of Longquan converter station is summarized, the fault reason is analyzed, and the problem in operation and maintenance of HVDC control and protection system is pointed out. Based on above analysis results, the technical transformation scheme is proposed. The scheme can not only solve the defects and problems of Longquan converter station HVDC control and protection system effectively, but also play a certain reference role for guiding construction, operation and maintenance of others HVDC project.