In the wind turbine control system， most control strategies are based on the stability of the sensor output signal. Once the sensor is damaged， it will affect the units security and efficiency， and even affect the quality of grid-connection. In order to improve the fault tolerance ability of direct-drive wind turbine， a dynamic reconfiguration control strategy of machine-side converter control system is proposed. According to the status change of the rotor position sensor， the mode with or without sensor is reconstructed dynamically in the control system. And the continuity and consistency are realized during the reconstruction process based on the Lagrange interpolation algorithm. Simulation results show that the steady-state performance of sensorless control mode is inferior to that of encoder mode. It can be run as a back-up mode conservatively during the sensor fault. The control method of reconstruction process proposed meets the requirements of continuity and consistency.