Face gear (hirth coupling) with high torque performance,automatic centering and high repeated accuracy, is widely used in highgrade CNC machine rotary table and other components. Traditional design for face gear is using manual approximate design method, then disc cutter is made according to the approximate tooth profile. The accuracy is limited by milling cutter and the precision of dividing head. The precise calculation formula for face gear tooth profile was derived and one domestic NC vertical grinding machine was reformed for face gear finish machining. It provides a feasible method.