Because of the complexity of the internal space structure and function diversity, personnel behavior in commercial complex, the load characteristics,plants operation and indoor environment are complex. Therefore, the chiller plants design and energy optimization need to combine their own characteristics. Firstly, through indoor thermal environment test to analyze the air conditioning demand of commercial complex, it is found that the indoor environment fluctuates more greatly compared with traditional commercial buildings, and there are significant differences among different commercial types. Secondly, the refrigeration system operation is analyzed through chiller plants operation records. It is indicated that the cooling load of commercial complex is relatively stable with the refrigeration system running for a long time, and the design capacity of the plants is generally too large. Finally, the load characteristics is analyzed through DeST modelling, and different chiller plants design optimization is compared. The result shows that the refrigeration system design method according to the commercial type load distribution is beneficial for energy efficiency, especially in the commercial complex with scattered commercial type layout and large difference in cooling load of different commercial type.