This paper tries to find out the changing regularity of chilled water by mathematical method Through measuring the change of chilled water's temperature after stopping the water chiller of air conditioning system installed in certain market According to the changing regularity,we can calculate the energy consumption at different time when the water chiller stopped before the close time of market The refrigerating capacity is also judged which obtained by chilled water when the water chiller stoppedAt last we discuss the excellent method by which the air conditioning system run non-continuouslyOur goal is to save energy consumption on the premise of keeping the fine quality of air conditioning