Abstract: Flameproof three-phase asynchronous motor is widely used in dangerous areas of offshore platforms. For this kind of motor, failure mostly occurs in bearings or bearing shells. On an offshore platform in Bohai, a medium-sized high-voltage flameproof motor was shut down normally and then restarted. In the restart process, the motor vibrated, showing a suddenly increasing current and abnormal noise. Inspection showed that there was no problem in the motor bearing, so plane shaft failure was considered. The reasons for the failure of the flameproof surface and shaft of the bearing chamber of the medium-sized high-pressure flameproof motor are analyzed, and the method of repairing the damaged motor's flameproof surface and rotor shaft is described.