In this paper, a novel thermally driven pump is introduced, and its test in a closed supercritical CO2 loop cycle system is studied. The thermally driven pump is a refrigerant-circulating pump composed of two expansion tanks, which has less electricity consumption and better reliability compared with conventional mechanical pumps. Experimental results showed that the system efficiency of the present thermally driven pump in the supercritical CO2 loop can be enhanced compared with that using the mechanical feed pump. In addition, it was found that the system efficiency with the thermally driven pump decreases with the outlet temperature of condenser. The thermal energy utilization efficiency of the loop system with the thermally driven pump can be increased when the condenser has higher efficiency. Copyright © 2012 John Wiley & Sons, Ltd.