In view of the influence of DC circuit of HVDC transmission between two poles, the principle of mutual inductance between the lines is applied, the electromagnetic coupling mechanism of high voltage DC transmission line and disturbance characteristics are studied, the electromagnetic coupling component of two DC line Binjin HVDC is calculated. The simulation model is established by RTDS, the time of dissociation in line failure, the distance between lines and the current fluctuation rate, which has an effect on control system is studied. Combined with the actual line fault waveform, optimization solution of Binjin DC is proposed. The optimized control strategy can reduce the effects of the non-fault pole to the minimum when restarting, which is verified by the RTDS simulation. The bipolar blocking is prevented effectively, which is of great significance on the safety and reliability in the operation of the power grid.