In order to solve the problem of excessive temperature rise caused by 2.5 WM permanent magnet wind turbine in operation, this paper designs a heat dissipation system. The combination structure of the heat exchanger and the heat sink was determined, as well as the heat dissipation method of the internal and external cycle isolation heat exchange. The control method and operation mode with Siemens PLC as the core are put forward. The computational fluid dynamics method is utilized to design the air-cooling heat exchanger and the liquid-cooled heat sink of the heat dissipation system. The results show that the cooling pipe gap has a great impact on the liquid cooling effect. The cooling pipe arrangement and piping arrangement of the air-cooled heat exchanger and liquid-cooled radiator are optimized. Finally, taking a 2.5 MW direct-drive permanent magnet wind turbine as an example, four environmental temperatures were selected to test generators in rated power. Verify that the cooling system is designed to meet cooling requirements. (c) 2020 Published by Elsevier Ltd.