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 of $NH_3$ refrigeration system by the superheat control for improving the energy efficiency. The experiments are carried out for the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa and for degree of superheat from $0^{circ}C;to;10^{circ}C$ at each condensing pressure. As a result of experiment, when the degree of superheat is $0^{circ}C$ at each condensing pressure, the refrigeration system has the highest performance.