To solve the problem that the PSASP built-in generator model can’t express the actual operating characteristics of direct-driven permanent magnet wind turbine(D-PMSG)in large-scale wind farm system, a simplified D-PMSG based on PSASP user custom model(PSASP/UD)has been built. The influences of generator and machine side converter are ignored by the transient simplified model of permanent magnet direct-drive fan. Considering the characteristics of the dynamic short circuit current during low voltage ride-through, the voltage frequency protection control and the active recovery rate setting, the transient simplified model is taken as a controlled current source with low-voltage protection characteristics and important parameters are optimized based on genetic algorithm. By comparing the D-PMSG transient simplified model with the detailed model, increasing the active recovery rate setting, and comparing the measured operating data of the single-machine test system under three-phase short-circuit fault condition, the correctness of transient simplified method for the permanent magnet direct-drive fan has been verified, and the parameter optimization method is also validated.