In an AC/DC hybrid power system, after the long-term power impact caused by large capacity High-Voltage Direct Current (HVDC) line blocking, the generators in the sending-end system will have different degrees of acceleration movement, and finally the generators at the sending-end may be out of step. This paper examines the generator tripping strategy after the HVDC line blocking fault. First, we analyze and compare the different effects on the stability of the sending-end system between the HVDC blocking fault and the short-term power impact, and then a triangle approximation method is proposed to estimate the generation capacity to be tripped. This establishes the conservative of calculated control variable. Then, the sensitivity of generator tripping is defined from the perspective of deceleration energy. Finally, considering the generator tripping ratio limitation, a scheme to allocate the generator tripping capacity is formed. Simulation and analysis of a typical two-area AC/DC hybrid power system are carried out to verify effectiveness of the proposed method. Using this method, the generators that have better capacity to enhance the need for transient stability to be considered as a priority. In this way the tripping amount and the control cost are effectively reduced. This work is supported by the National Natural Science Foundation of China (No. 51637005).