In this paper, the characteristics of a special condenser for space thermal control were investigated. In order to compare the thermoresistance getting from different formulas, both single-phase and two-phase fluid in the condensers were calculated. The results present that the thermoresistance has a uniform value for single-phase and a large variance for two-phase fluid. Therefore, experiences were performed to clearly comprehend two-phase fluid performance in the condenser. From the experiments, it demonstrates that the condenser thermoresistance has decreased with the heat load increasing under the same mass flow rate. The analyzes points out that the thermoresistance caused by contact plays a more importance role for the condenser heat rejection capacity.