Abstract: The general expressions for some important thermodynamic parameters of gases in an arbitrary process,which include the heat capacity,expansion coefficient,pressure coefficient and compressibility,are derived.The equation of state of the van der Waals gas and the generalized Redlich-Kwong equation of state are used to discuss the thermodynamic properties of real gases in some concrete processes.The results obtained can be used to derive not only some important contents in literature but also some new significant conclusions.