Abstract: The phase behavior parameters such as gas deviation factor Z，density and the change with different CO₂ content are studied by means of experiment，the physical factors such as pressure and temperature which influence phase behavior change complicatedly along wellbore，the factors if associated will result in more change，which can not be tested one by one，to the gas wells with different CO₂ content the calculation model of temperature and pressure for conventional gas well，as well as different CO₂ content phase behavior equation，is used to modify deviation factor，the distribution of pressure and temperature is calculated with numerical method through programming non-linear equation，then，the phase behavior parameter deviation factor Z and the distribution of density are calculated.The phase behavior of gas well with rich-content CO₂is researched through related case study，it is recognized that the flowing gas collum with rich-content CO₂ in different wellbore section forms saturated steam phase，under saturated steam phase and gas phase，liquid phase and gas liquid transition phase are formed while the distribution of gas phase is static，there is the reversion phenomenon of heavier upper part and lighter lower part in gas phase，a comparison is made between experimental result and field testing result，the phase behavior characteristics are basically consistent.

Key words: rich-content CO₂, density, deviation factor, calculation, experiment