The participation of wind turbines (WTs) with the integrated inertia control (IIC) in frequency regulation can significantly support the frequency dynamics and improve the frequency stability of the power system with high proportion wind power. However, the speed recovery stage of WTs after exiting frequency modulation may cause the problem of secondary frequency drop, which will cause a secondary impact on the system frequency. To optimize the frequency regulation effect of WTs, an optimization method of frequency regulation parameters of WTs based on particle swarm optimization (PSO) is proposed. Firstly, the influence of the parameters of the IIC on frequency regulation results is analyzed. Secondly, the objective and constraint of frequency regulation optimization considering the second frequency drop are proposed. Finally, the PSO is used to solve the optimal the parameters of the IIC. The simulation results show that the parameters optimized by PSO have a better frequency regulation effect.