The purpose of this study is to realize a non-condensing environment by developing a new type of desiccant air-conditioning system with lower energy consumption. In this paper, a displacement air-conditioning system with a desiccant outdoor air-conditioning unit is proposed and the overall energy efficiency of this system is compared with that of the conventional outdoor air-conditioning system. The results show that the system COP of the proposed system is considerably higher than that of the conventional outdoor air-conditioning system.