Watercooled motor has wide applications, and its design shows some special features. For the two water jacket structures of the watercooled motor, i.e., Zshaped axial water jacket and circumferential spiral water jacket, the advantages and disadvantages were introduced, and the calculation methods for the design parameters were given. Considering the pressure on the water jacket, the strength calculation formulas were derived for the inner and outer shell walls. This research could give reference for the design of watercooled motors.