Abstarct: That we can calculate thermodynamic properties of hydrocarbons and mixtures like natural gas in industry and scientific is important. Natural gas is a complex mixture of various hydrocarbons and gases like nitrogen and carbon dioxide. Thermodynamic properties related to molar mass, forces between molecules and phase bihaviour. Equation of state is the cheapest ways to determine thermodynamic properties. Therefore enormous of EOSs have been represented by scientists. Recently, statistical thermodynamic has been developed in determining thermodynamic properties on molecular basis. PC-SAFT is a customary equation of state in literature which was calculated in papers. In this study, thermodynamic properties have been calculated using PC-SAFT for pure components and mixtures.Calculations have been validated with experimental data in literature. Validations show that PC-SAFT EOS has high accuracy calculation thermodynamic properties of natural gas. Natural gas properties have been changed from extracting to use, also knowledge of phase behavior is very hard. In this study we try to calculate thermodynamic properties in high pressure and low temperature. We determined density, enthalpy, entropy, internal energy, isochoric heat capacity and isochoric heat capacity and compare with experimental data. After we had found that our results of PC-SAFT are acceptable, we calculated thermodynamic properties of Semnan province.