Connecting the regional power grid through HVDC makes the DC interconnected asynchronous power grid appear in the system, which weakens the mutual support ability between the regional power grids. Aiming at the frequency adjustment problem after the power disturbance occurs in the regional power grid, the cooperative power allocation method of HVDC and AGC is proposed in this paper. Firstly, the frequency adjustment model of power system and the control strategy of HVDC participating in primary frequency regulation are introduced. Secondly, the method of cooperative power allocation between HVDC and AGC is designed based on the consensus algorithm. In the secondary frequency regulation stage, the adjustment cost of each unit and HVDC is considered, and the power allocation algorithm is designed with the adjustment cost as the consistency state variable to realize the cooperative control of HVDC and AGC. The adjustment enables the connected asynchronous power grid to bear part of the power imbalance according to the adjustment cost and reduce the overall adjustment cost of the interconnected system. The effectiveness of the proposed method is verified by an example.