The application of the compressed natural gas(CNG) system has been a effective portion of enormous technical efforts to cope with the environmental regulations that have been carried out, because of its excellent fuel efficiency and low pollutant emissions. The main objective of this paper is to investigate the performance characteristics of the CNG regulator as one of the CNG fuel supply system, which depressurize the highly pressurized CNG. The experimental results demonstrate that the precisely controlled coolant temperature and flow-rate are one of the most effective technology to enhance the fuel consumption efficiency and the low emissions. On the CNG regulator performance test, we could give variety to the air inlet pressure and the air outlet flow-rate, respectively, bringing on the coolant temperature and flow-rate. The evaluation of the dynamic response and the creep characteristics on working fluid were experimented on the air inlet pressure of 100 bar, 150 bar, 200 bar, 250 bar, respectively, at the air outlet flow-rate of 0 to 70 LPM and the coolant flow rate of 3 LPM, 6 LPM.