The random search strategy was substituted by the chaotic traveling strategy in standard simulated annealing algorithm, variance evaluation criteria was appended as a condition to stop searching, a special method was adopted to determine the initial temperature in order to reduce redundant iterations, the improved stimulated annealing algorithm was applied to minimize the total power consumption of the multiple chiller water units which connected in parallel to achieve the purpose of energy saving. The mathematical model of the multiple chiller water units and the energy-saving methods by means of the improved simulated annealing were established. Both the theoretical analysis and the actual results indicated that the energy savings could be realized, and the total energy consumption of all the chillers was reduced by 4% to 11% compared with the usual load distribution strategy.