Abstract: Temperature and humidity, as important indexes of the human body's comfort, are important in the research of air flow organization of hydropower stations. By field test and numerical simulation, the field test data of generator floor of a main pumped powerhouse is analyzed. It is found that the distribution of temperature field in generator floor is not uniform in space due to the differences between the heat source layout of generator floor and the outlet temperature of air conditioner. Then an optimized scheme for adjusting the cooling water flow of the air conditioner is put forward to indirectly control the outlet air temperature of the air conditioner for improving the temperature uniformity of the generator floor. Thereafter a CFD numerical calculation of temperature field in generator floor before and after optimization is carried out. The reliability of the calculation model is verified. The comparison of the calculation results before and after the optimization shows that the optimized scheme can well improve the temperature uniformity of the generator floor.