Since the use of CFC and HCFC refrigerants are to be restricted due to the depletion of ozone layer, this experiment applies the NH$_3$ gas to study the performance characteristics from the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 14.5 bar to 16.0 bar by 0.5 bar and for superheat temperature from $0^{circ}C$ to 1$0^{circ}C$ by 1$^{circ}C$ at each condensing pressure. As a result of experiment, when the superheat temperature is 1$^{circ}C$ at each condensing pressure, the refrigeration system has the highest performance.