Abstract: As the penetration rate of renewable energy in the power system gradually increases, the instability of the power system also increases, and the problem of system inertia estimation becomes particularly important. Therefore, this paper proposes an inertia estimation method for power systems containing wind power and photovoltaic. Firstly, by analyzing the principle of inertia in power systems containing wind power and photovoltaic, an overall parameter identification model considering the fast time-varying characteristics of wind and solar power is established. Then, based on the recursive least squares method with forgetting factors, the model is solved to estimate the system inertia. Finally, a simulation system of three machines and nine nodes containing wind power and photovoltaic is built on the MATLAB/Simulink platform to verify the effectiveness of the proposed method.