Abstract: The paper gave topological structure of permanent magnet direct drive type wind power system, analyzed working principle and topological structure of DC unloading circuit, established model of permanent magnet wind power system, and constructed simulation model of low-voltage ride through technology of permanent magnet direct drive type wind power system based on DC unloading circuit on Matlab/Simulink platform. The simulation result proved feasibility and good ride through capability during low-voltage ride through of the system. The system is foundation of product realization.