A new type of condenser with gas-liquid separator is designed based on the short-tube effect. The innovation of the new condenser is the discharge of condensate liquid by different-sizes seepage holes. The holes are opened on the pass partition plates of both sides of the condenser, so the steam quality and velocity can be maintained at a high level for next tube pass, and consequently the heat transfer intensity is improved. The liquid layer is formed on the pass partition plates by a reasonable design of the seepage holes, which is used to separate the gas and liquid, so the liquid could be discharged through the seepage holes and the steam could only enter to the next tube pass. The working fluid in the tube is R245fa, and the heat transfer fluid in the shell side is cooling water. Contrast test has been done to evaluate the thermal performance of the new designed condenser with the vapor flow rate ranging from 100~115 L/h. The results show the new type condenser operates with higher heat transfer coefficient and better overall thermal performance. The heat transfer coefficient is 4.3~7.0% higher than the traditional one. The conclusions obtained in this study verify the theory of short-tube effect and provides experimental data and references for the development of high efficient heat exchanger.