CO2 has perfect environmental properties and has great potential to become a very ideal working fluid for power cycle. In the laboratory, a CO2 transcritical power cycle system was established, using a rolling piston expander. Experimental study was carried out on the operating parameters, the electric power generated and the thermal efficiency. The pump operating speed and the load resistance were used to regulate the operating parameters. The results showed that there was a sudden decrease for the electric power generated in the start-up process. The electric power rose with increasing the converter frequency. When the converter frequency kept constant, the electric current declined with increasing the load resistance. In the experimental study, the steady electric power generated could reach about 1100 W and the thermal efficiency 5.0% when the high pressure was about 11 MPa and the low pressure was about 4.6 MPa. Though the isentropic efficiency, about 21.4%, was unsatisfactory, it still has important significance for the study on CO2 expander. (C) 2015 Elsevier Ltd. All rights reserved.