A method to determine the condensing temperature set point of air-cooled refrigeration system with an electronic expansion valve was discussed in this paper. This set point is fixed for a specific system and is based on the flow characteristic of the installed electronic expansion valve in variant opening and pressure drop. As common sense, at constant differential between condensing pressure and evaporating pressure, larger opening of expansion valve allows more refrigerant flowing through the expansion valve into evaporator. This feature offers an opportunity to lower the condensing temperature via increasing opening of expansion valve to enhance refrigeration efficiency and in the same time designed cooling capacity can be maintained at low ambient temperature. In this case it is supposed that the installed electronic expansion valve’s capacity was larger than the evaporator’s, and in fact that occurs frequently in refrigeration system designing. The benefits of this method could include: the capacity of electronic expansion valve is fully utilized, the refrigeration system will operate at a lower condensing pressure and the power consumption of compressor can decrease, hence the improvement of system efficiency is predictable.