The objective of this paper was to study energy saving possibility of DVM air conditioning system compared to all-air system with constant air volume and primary air fan-coil system. Three office buildings are selected to study the impact of outdoor air temperature and air-conditioning load on energy consumption of the above three systems. eQUEST was used to simulate the annual building performance. The simulation results indicate that energy saving potentiality of DVM air conditioning system is significant under part load condition because of its indoor unit independently controlled characteristic and good regulating characteristics; for office building with boundary condition in standard GB 50189-2005, energy saving potentiality of DVM air conditioning system is significant when building area is less than 20,000m(2), or primary air fan-coil system with two sets of water source screw chiller is more available. (C) 2014 Elsevier B.V. All rights reserved.