A winding method for a stator module applicable to a motor having z slots, 2p poles, and m phases. The stator module includes a stator core and a winding coil. The winding coil is made of a flat wire. The winding method includes: forwardly winding some stator slots by means of the arrangement and connection of multiple U-shaped conductor sections, and then reversely winding the stator slots; afterwards, forwardly winding the remaining stator slots, and then reversely winding the stator slots; and cycling in this way.