The random fluctuation of load and new energy output affects the active power balance and frequency stability of power grid. The conventional synchronous generator with large capacity participates in frequency regulation, but the response speed is slow. As a new power source, fuel cell(FC) has a small capacity and is not suitable for balancing active power, but it is flexible in operation and fast in response, so it is possible to be used for power grid frequency regulation. Firstly, this paper establishes a power flow model with FC. Then after introducing the droop control of active power, a dynamic power flow algorithm with fuel cell participating in primary frequency regulation is proposed. In order to simulate the response delay of FC, the inertia link is considered in the dynamic power flow. The frequency regulation effect is improved by introducing a rapid discharge of DC capacitance. The example analysis gives the results of dynamic power flow, analyzes the effect of FC output delay and DC capacitor discharge on the frequency regulation results, and verifies the effectiveness of the proposed algorithm.