The wind turbine provides virtual inertia to the system, which can effectively improve the inertia level of the power system. However, the problem of quantitative evaluation of the effective support capability of the virtual inertia of the wind turbine needs to be further studied. Therefore, this paper proposes a quantitative evaluation method for the effective support capability of virtual inertia of wind turbine. Firstly, the system frequency response (SFR) model of power system with wind turbine is constructed. By comparing with the traditional SFR model of power system, the concept of inertia efficiency factor is proposed, and the corresponding relationship between virtual inertia of wind turbine and inertia of synchronous machine is established from the perspective of frequency response index. Secondly, considering the influence factors such as the control parameters and response delay of the virtual inertia of the fan, the expression method of the inertia efficiency factor is proposed, and then the evaluation expression of the effective support capability of the virtual inertia of the wind turbine is derived. Finally, the simulation verifies the effectiveness of the proposed method.