As halocarbon refrigerants, HCFC22 and HFC134a are widely available for commercial air-conditioning applications and HCFC22 is the predominant refrigerant in use today. HCFC22 equipment is being specified today in well over one-third of all large tonnage chiller applications in the world, and all large reciprocating water chillers produced in China are HCFC22 installations at present. According to the Copenhagen Amendment to the Montreal Protocol, HCFCs (including HCFC22) are to be phased out completely before January 1, 2030. It is therefore of great importance to develop new water chillers utilizing alternative refrigerants, applied in the air-conditioning system of nuclear power stations. In this work, the physical properties, the refrigeration cycle characteristics and the system characteristics of HCFC22 and HFC134a are compared and analyzed in detail. On the basis of this, technical matters of using HFC134a as the substitute for HCFC22 on water chillers applied in the air-conditioning system of nuclear power stations are discussed.