The application of evaporative cooling technology in the cooling of large wind power generator is a new attempt in the discovery of wind power energy. In some particular circumstances, the air-cooling condenser must be adopted as the secondary cooler in the evaporative cooling system of large wind generator. For the cooling medium in the air-cooling condenser is the air and the distribution of temperature is uneven along the cooling tube, so it’s necessary to do deep research on it. Experiments are carried out to study the heat transfer characteristics of the air-cooling condenser used in the Close-loop Self-circulating (CLSC) evaporative cooling system. The temperature distribution and the heat transfer can be acquired from the experiment. Thorough study is carried out on restart up of the close-loop evaporative cooling system of the wind power generator. Experiments are done in the laboratory and real wind power generator, and it’s found that there is a critical point in the restart up of the generator. Only if the flow head overcome the critical point can the wind power generator restart automatically. The result shows that heat transfer can be enhanced by some special method and the air-cooling condenser can satisfy the demand of the cooling system.