In order to avoid the asymmetric drop of grid voltage leading to the disconnection of doubly-fed Induction Generater (DFIG), the mechanism of DC bus voltage fluctuation of DFIG under asymmetric grid fault is analyzed. The phenomenon of DC side overvoltage is mainly caused by DC component of stator side and negative sequence component of grid voltage. The voltage and current equations of doubly fed induction generator in positive and negative sequence coordinate system are derived by coordinate transformation of reference frame. The mathematical model of DFIG in positive and negative sequence coordinate system is established. Using coordinated control method of machine and network converter, the negative sequence component of rotor current of machine side converter is controlled to zero during asymmetric grid fault, The converter adopts double closed-loop positive and negative sequence current control to suppress the negative sequence component on the grid side, and combines with power tracking control module to effectively suppress the double frequency fluctuation of electromagnetic torque and current, as well as the fluctuation of DC bus voltage and the negative sequence component of current, thus improving the dynamic performance of DFIG under asymmetric grid fault. The simulation results show the reliability of the control strategy.