Aiming at the problems of weak heat dissipation, low torque density and high winding temperature of permanent magnet outer rotor electric drum motor for belt transportation, a water cooling system based on 710 kW electric drum is designed. In the system, a three-dimensional field solution model by fluid-structure coupling method is established, and the solution calculation is performed. The influence of water channel configuration, water flow, outer diameter of water jacket, wall thickness, number of water channel and height on temperature rise is analyzed. By simulation analysis and temperature rise test, it is rerified that the designed water cooling system is beneficial to improve the heat dissipation capacity of the electric roller, which provides a reference for further improving the torque density of the electric roller.