Maintenance method of wind turbine generator set

The invention relates to a maintenance method of a wind turbine generator set. The wind turbine generator set comprises a tower, an engine room installed on the tower, and an impeller installed on the engine room, wherein the tower is fixed to a transport ship. The impeller and the engine room are sequentially demounted, and the engine room and the impeller are sequentially mounted so as to complete the maintenance of the whole wind turbine generator set, thereby lowering the maintenance cost and difficulty of the wind turbine generator set, and enhancing the economical efficiency and safety for constructing the wind field.