A large number of wind power, photovoltaic and other new energy equipment are connected to the power grid, and the system gradually presents the characteristics of low inertia, which will bring a series of frequency safety problems.Traditional frequency characteristic analysis methods are difficult to accurately grasp the changes in system frequency characteristics after the participation of new energy in inertia support and primary frequency modulation. In order to explore the frequency characteristics and situation changes of the system considering the contribution of wind power-photovoltaic-energy storage to frequency modulation, a new frequency response model is constructed based on the traditional frequency response model and the contribution of wind power-photovoltaic-energy storage to frequency modulation is defined. The frequency characteristic transfer function is used to set the parameters of the system frequency modulation unit. Then the frequency stability index of the power system is quantitatively analyzed, and the influence of the inertia time constant and the control coefficient of each frequency modulation unit on the frequency stability is analyzed from the angle of frequency domain. Finally, the theoretical analysis is verified by MATLAB/Simulink platform. The method of analyzing the frequency characteristics of the new power system from the perspective of time domain and frequency domain can accurately predict the frequency situation of the system considering the contribution degree of wind power-photovoltaic-energy storage frequency modulation, and provide guidance for the safe operation of the new power system frequency considering the inertia support of wind power-photovoltaic-energy storage and primary frequency modulation.