High permeability wind power integration leads to the equivalent inertia decline of the original system, which brings new challenges to the power system stability control after the system is out-of-step. However, there are few literatures that apply the Virtual Inertia Control (VIC) in the power system stability control after the system is out-of-step. This paper proposes a VIC strategy of wind power to improve the out-of-step oscillation modes. Under the VIC, the Variable Speed Wind Turbine (VSWT) modifies the active output basing on the frequency deviation of the wind power grid connection point. When the system is subjected to severe disturbances, the VSWT provides plenty of active power support to the system. The active power provided by the VSWT under the VIC inhibits the intra group power oscillation. It can realize the process of non-coherent to coherent, thereby improving the out-of-step oscillation modes. Simulation results prove the correctness and effectiveness of the VIC strategy. This work is supported by National Natural Science Foundation of China (No. 51507116) and Science and Technology Project of State Grid “Research on the Optimization of the Multi-level Grid Structure of the Planning Network considering the Third Line of Defense”.