To improve the stability of power grid with permanent magnet direct-driven wind turbines， the operational characteristics of permanent magnet direct-driven wind turbines under grid faults is studied. A low voltage ride-through（LVRT） control strategy is proposed for the direct-driven wind turbine using a back-to-back pulse-width modulation（PWM） converter. The electromagnetic power of the PMSG is limited under the grid faults to minimize the power transferred to the DC-link capacitor and grid-side converter. The generator power information is used in the current closed-loop control of the grid-side converter to realize the stable control of the DC-link voltage. The simulation results show that hardware protection apparatus is not necessary and the proposed LVRT operation can be effectively realized under symmetrical and unsymmetrical faults.