An example of a central air-conditioning project of a rebuilt department store is described in this paper. The design of air system, water system, layout and operations for the air conditioning system is presented in this paper. The system is different form ordinary ones because the floor height is lower; so many special considerations must be taken during the design. In addition, the low cost and easy maintenance place an important role in the design. The operational result of the design is promising and it can be referenced by other designers.