Abstract: Complex phase change and re-distribution exist in gas condensate reservoir. It will produce gas condensate in
formation and the wellbore，respectively，when the pressure drop to below dew point pressure，resulting in the conversion
of mass between wellhead and bottom hole in gas production and oil production，but still follows the law of conservation of
total mass. Therefore，according to mass conservation principle，we established the oil and gas two-phase flow equations. By
introducing the two-phase pseudo-pressure function，unstable deliverability equation was derived. On this basis，we fit the
entire history of production by taking material balance equation and production data into consideration. With this method we
not only get the current gas production，but a variety of formation pressure and formation parameters. An example is then
analyzed to verify the accuracy and reliability，the method is conducive to the promotion the use of gas condensate.

Key words: gas condensate reservoir, two-phase pseudo-pressure, material balance, production, reserve