Abstract: In order to reduce the risk of subsequent commutation failure in HVDC transmission system, the commutation failure mechanism is analyzed, and combined with symmetrical and asymmetric fault detectors, an improved scheme of current deviation control which can be adjusted according to the severity of fault is proposed. The suppression effect of the slope of current deviation control on commutation failure is analyzed. It is found that the larger the slope of slope function in current deviation control is, the more sensitive it is to input current deviation, and the larger the commutation margin increment is, the more conducive it is to suppress subsequent commutation failure. Finally, the proposed control scheme is realized on the basis of CIGRE HVDC Standard Test System in PSCAD/EMTDC simulation software. The simulation results show that the current deviation control method proposed in this paper can effectively reduce the risk of subsequent commutation failure of HVDC system and improve the operation characteristics of HVDC system.