A 65 kWh liquid-cooled power battery system for a pure electric commercial vehicle was taken as the research object, and a thermal management test bench was independently designed and built, focusing on the comparison of cooling effect of the thermal management system on battery temperature under different ambient temperatures and working conditions. It was found that although the thermal management system can control the battery temperature to be within an appropriate range, the energy consumption in a high-temperature environment was higher. Therefore, the thermal management control strategy was optimized. The optimized control strategies were superior to the original control strategy in terms of battery cooling effects and energy consumption, and the energy was saved by 37.78% and 78.63% under high-temperature high-speed working condition and comprehensive urban working condition, respectively, indicating that the energy efficiency of thermal management was significantly improved.