This work studies the level-set based topology optimization for the optimal layout of winding in electric motor. The functional to optimize is to maximize the torque in the air-gap. The coil domain is initiated by a level set function. The time evolutionary equation is used to update the function. The level set model forms clearly the dynamic boundaries between the conductor and the insulation which determine the optimal distribution of coil by means of the topological changes. This proposed optimization strategy is applied to the winding of a Permanent Magnet Synchronous Motor. An optimal layout of coil is generated from this proposed method.