The cooling tower is often overlooked in the air conditioning system, but it impacts on the heat dissipation of system. This paper tests and researches the influence factors of cooling tower performance. First, we analyzed the cooling tower efficiency, cooling capacity and others of an actual air conditioning system. Then we studied the relationship between air/water ratio, inlet air quality and flow rate and the cooling tower performance. The results show that the air/water ratio have a linear relationship with the cooling tower efficiency, and the quality and the flow rate of inlet air have a greater impact on the cooling capacity and cooling water contrast method. This paper has an certain significance on the diagnosis and energy efficiency improvement of cooling towers.