Due to the small capacity of the converter, the doubly fed induction generator wind turbine system is limited in its operation ability under grid faults, especially grid voltage sags. This paper mainly studies the control strategy of the DFIG wind turbine system under grid faults. First, the characteristics of the DFIG system under grid voltage sags are analyzed, and then the protection and control strategies of the DFIG system under grid faults are proposed, which mainly include pitch angle control, rotor overcurrent protection, and oscillation damping control. Finally, it is proposed to add a third-level control scheme, which includes a damping controller, a rotor side voltage controller, and a grid side reactive power compensator. This control strategies can improve the voltage support capability of the DFIG system under grid faults. The simulation results prove the feasibility of the proposed scheme.