Due to the increasing penetration level of wind power in power system, wind turbines can provide less frequency support than conventional generators due to their small rotor mass. This makes the power system with low inertia and hence cause frequency problem. This paper has proposed an integrated control strategy for participate in primary frequency control by doubly fed induction generation (DFIG). According to the reserve capacity required for primary frequency control, a de-loading control method is also proposed in this paper to resolve the issue of inertia control and primary frequency control. Based on the analysis method of the frequency control characteristics of DFIGs, the frequency control strategy can adjust the static frequency difference coefficient and it is proposed by improved variable pitch control method. Furthermore, the virtual inertia control and the primary frequency control can be integrated a control strategy of DFIGs. The simulation results show that the DFIGs can provide an effective inertia support to reduce the system frequency changing rate in the inertia process and improve the static frequency stability of power system by the static frequency characteristics.