Abstract: In this paper, the 1000 MW generator of a power plant is subjected to the pressure test.The insulation is damaged due to the oil entering the vent pipe of the generator outlet pipe and the high temperature of the stator outlet pipe, resulting in insulation breakdown of the generator.The author puts forward and implements the installation of anti oil device to avoid the oil inlet, plug and plug air channel solution.This method has certain reference value for similar faults of the same type generator, and is of great help to reduce the workload.