On the basis of typical climate data in Tianjin and thermal parameters of building envelope, TRNSYS software is utilized to numerically simulate and capture annual dynamic cooling load of buildings serviced by south region district cooling system in Tianjin Cultural Center. According to the operation control strategy of the system in different part-load ratio, it is calculated cooling capacity and electricity consumption of refrigerating unit, electricity consumption of pumps, cooling loss of heat changers and pipelines. Thus theoretical energy efficiency ratio of the district cooling system in different cooling load ratio can be captured. During July 31, 2012 to September 16, 2012, the system’s operation energy efficiency is tested, which is relative difference 3.3% compared with theoretical calculation result of the counterpart cooling load. The result shows that factors which influence system energy efficiency are focused on part-load ratio, energy efficiency of refrigerating units, electricity consumption of pumps and cooling loss of pipeline. Along with the decline of part-load ratio, the system energy efficiency decreases obviously. Each pump in this project adopts vary-frequency regulation, which energy-saving effect is remarkable. Part-load ratio has a little influence on pump energy consumption, and along with the decline of part-load ratio it increased slightly. But the cooling loss, caused by heat exchangers, pipelines and temperature rising of water pumps, increases along with the decline of part-load ratio.