With the large?scale grid connection of new energy and participating in system frequency modulation through virtual synchronous generator (VSG), virtual inertia has become an important component of system inertia. Therefore, an equivalent inertia evaluation method of power system considering the virtual inertia of new energy is proposed. Firstly, a unified analytical model of new energy VSG equivalent virtual inertia and synchronous generator moment of inertia is established. Secondly, the controlled autoregressive model is used for dynamic modeling and the problem of inertia solution is transformed into the problem of parameter identification in the model. Then, using the active power frequency time series data, the parameters to be identified in the model are solved by adopting the adaptive recursive least square algorithm. The adaptive forgetting factor is introduced and dynamically adjusted to realize the continuous tracking of the system equivalent inertia under different working conditions. Finally, the simulation analysis is carried out on the IEEE?39 bus system. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the identification method.