In order to better guide the wind generator design, a 3 MW air-air cooled doubly-fed wind generator is taken as an example for the research of flow and heat transfer characteristics. Based on the theory of hydromechanics and numerical heat transfer, the 3D fluid flow and heat transfer coupled physical and mathematical models are established according to the model of air-air cooler and wind generator. Fluent software is used to numerically simulate the steady 3D flow and temperature fields of the wind generator under rated working conditions with given fundamental assumptions and boundary conditions, and the experimental data of winding temperature rise are obtained by adopting resistance and embedded temperature detector (ETD) methods under the same working conditions. It is found that the error is within 5 K between the numerical simulation results and experimental data, indicating that the numerical method is credible. Finally, the distributions of the wind generator flow and temperature fields are analyzed, and the flow rate of the 18-vent motor is calculated in detail. This method provides a theoretical support for the simulation and optimization of new wind generators.