The VCRS (vapor compression refrigeration system) was applied as a subcooler to obtain the needed temperature of a cryoablation system by J-T effect,and a mathematic model based on the first and second laws of thermodynamics was established for the energy and exergy analysis using R134a,R22 and R404a in the subcooling system of the cryoablation system.The effects of the evaporator and condenser temperatures on the COP,total exergy destruction and total exergy efficiency of the system were investigated.The exergy destruction and exergy efficiency in different system components were also displayed.The R134a and R404a systems have lower COP and exergy efficiency but higher exergy destruction compared to the R22 system.However,the performance of R134a system is closer to the R22 system.So,the best refrigerant is R22 and R134a is a good alternative to R22.The major exergy destruction occurs in the compressor,condenser and capillary tube among all system components.The reasons and improvement suggestions were presented.