On the basis of the security system original function, the Jinbei-Nanjing HVDC project increases a new recognition method of power loss, when sequential manual outage and fault tripping occur in a short time. In the event of continuous power loss, safety control system can accurately identify it and then act, the new control strategy makes the safety control system more perfect. The paper introduces the composition and function of frequency control system of East China in detail, also introduces what action strategy should be taken when the power shortage is caused by the blocking of one of the HVDC lines. The effectiveness and accuracy of the East China frequency coordination control system and its control strategy are verified by the system test, and the optimization suggestions on the shortcomings of current frequency association control system are proposed. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52094016000X).