In this paper three perfect gas models with constant specific heat or with variable specific heat and one real gas model based on the gas property tables are respec- tively considered to implement into the three-dimensional CFD (computational fluid dynamics) analysis of a centrifugal refrigeration compressor stage. The results show that the gas models applied to the CFD code have significant influences on the performance of stage and the flow structures in the stage. Although the ther- modynamics operating condition of evolving fluid in the centrifugal refrigeration compressor has a significant deviation from the perfect gas, the perfect gas model with the modified value of gas constant and the variable specific heat offers a good prediction of stage performance. To predict some basic fluid flow parameters and flow structure accurately, the real gas effects should be considered and the rea- sonably accurate thermodynamic properties based on the analytical gas equation of state or numerical interpolation of gas tables should be applied to the CFD code. In this paper three perfect gas models with constant specific heat or with variable specific heat and one real gas model based on the gas property tables are respecively modified to implement into three-dimensional CFD (computational fluid dynamics) analysis of a centrifugal refrigeration compressor results. The results show that the gas models applied to the CFD code have significant influences on the performance of stages and the flow structures in the stage. Although the thermododynamic compressor has a significant deviation from the perfect gas, the perfect gas model with the modified value of gas constant and the variable specific heat offers a good prediction of stage performance. To predict some basic fluid flow parameters and flow structure accurately, the real gas effects should be considered and the rea- sonably accurate thermodynamic properties based on the analytical gas equation of state or numer ical interpolation of gas tables should be applied to the CFD code.