With the increasing penetration of renewable energy and the large-scale application of HVDC, the ability of inertia response and primary frequency response in the power system is weakening continuously, threatening the frequency stability of the power system. The current research work is mainly focused on the estimation of inertia response, the design of control strategies for inertia response and primary frequency frequency, and no research has been conducted on the estimation of primary frequency power in the power system. Therefore, this paper proposes the estimation of primary frequency power based on the estimation of inertia response supporting power. First, the process and scope of the frequency response in the power system are described. Then, the support power provided by the inertia response of the power system is estimated in the disturbance. The curve of primary frequency power is calculated and draw based on the estimated support power. Finally, the simulation analysis is performed in Digsilent Powerfactory using 10-machine 39-bus as an example to verify the validity of this paper.