Abstract: The volumetric specific heat capacity and isobaric heat capacity of real gases were calculated using perturbation theory in statistical thermodynamics and the accuracy was improved by using an improved method inthis paper. The calculation of numerous points of the saturated and superheated vapor of real fluids such as N2, O2,SO2,CO,CO2,CH4,C2H2, C2H4, C2H6, C3H8, etc., showed that the results were in good agreement with the values reported in literature and improved accuracy was achieved in comparison with the general L-K equation of state and the equation of specific heat capacity in literature. The specific heat capacity at constant volume and the specific heat capacity at constant pressure of real gases at a given state can then be calculated only when the critical parameters Tc, Vc and acentric factor are known. Although this method is not fit for direct calculation for its complexity, it is efficient, simple and practical in computerized calculation.