A natural and environment friendly refrigerant propylene and propane are proposed as the substitute of R22 in air conditioner. The experiments were respectively conducted on an existing enthalpy potential lab. Refrigerant charge was held at the constant superheat condition. It is founded that the cooling capacity of R1270 was 96% of R22 system while the R290 was 92% of R22 system, but the COP bother higher than the former system, the refrigerant charge of R1270 was reduced 56.8% of R22 while R290 was 58.4%. With the condensing temperature increased, the system’s cooling capacity is gradually reduced, the cooling capacity of R1270 and R290 are decreased faster than R22, this indicate that R1270 can improve the running performance of system and has more advantages than R290 as substitute for R22, if do some improvement to the original system, can obtain a better results.