Abstract: As the core of a wind turbine, the motor is very important for long-term safety and stability.When a 2 MW permanent magnet synchronous generator(PMSG) in an extreme weather of typhoon was coming, the brake failed, and the brake disc could not be released, resulting in sharp wear of the brake disc.The brake disc was located in the motor shafting.In order to determine whether the fault caused damage to the motor parts, the motor was removed from the shelf and returned to the factory for dismantling, inspection and maintenance.This paper measured the actual size of the motor parts after disassembly and used finite element analysis method to review the deformation of the shaft with differences in measurement, analyzed the impact of the continuous operation of the motor on the shaft under the closing condition of the brake, and found that the shaft of the motor was deformed, and the brake disc was seriously worn, making it impossible to continue to use.It provides a reference value for determining the design parameters of PMSG and monitoring the operation and maintenance of the wind farm.