The phenomenon of "secondary commutation failure" in the process of fault recovery for the HVDC system with STATCOM is described and reproduced. The relationship among STATCOM reactive power compensation, HVDC system control characteristics and fault degree is analyzed. The research shows that the existing STATCOM reactive power control strategy will deteriorate the system recovery characteristics when serious AC side faults occur. Furthermore, an improved STATCOM transient reactive power control strategy is proposed,which can allocate reactive power compensation mode of STATCOM differently according to the fault level. Finally, the proposed control strategy is simulated in PSCAD/EMTDC. The simulation results show that the proposed control strategy can effectively reduce the probability of secondary commutation failure and significantly improve the recovery characteristics of the system.