To make sure of the heating transfer and safe running of mine explosionproof motor which had special structure and applying situation such as small size, high power and terrible heat, it’s the key to design a rational and suitable watercooled structure. A program based on the heat transfer and hydrodynamic theory was compiled in this paper research on the watercooled structure and temperature rise of the YBSD motor. The calculation result was compared with the case and date from actual motor, then the feasibility and accuracy of the calculation method was verified, which provided a technological means.