The thermodynamic properties of the ternary mixture refrigerant HFC 32/HFC 125/HFC 134a as a replacement of HCFC 22 have been calculated using CSD state equation, with adequate mixing principle and interacting factors. Error analysis shows the good accuracy of the calculation. Based on the calculated results, the theoretical cycle has been further calculated, analyzed and compared. All of them have been programmed and operated in the computer.