A novel integrated system of vapor compression and pump-driven two phase loop for energy saving in data centers cooling is presented in this paper. In the new system, the vapor compression mode works at the hot outdoor temperature and the pump-driven mode operates at the cold outdoor temperature. An experimental bench was constructed using a 3 HP compressor and a 1 HP compressor in the integrated system, respectively. The results show that, the new system has a better performance for application in data centers, the maximum cooling EER of the integrated system can reach to 29.71. The most suitable outdoor temperature for switching the modes was also obtained from the experiment. It is recommended to design the integrated system based on the cooling performance of the pump-driven two phase loop. (C) 2015 Published by Elsevier Ltd.