During the well produces in lowpermeability gas reservoir, it appears the gas and water two-phase flowdue to the existence of edge water, bottom water and interlayer water. The reasonable productivity is associated with kinds of development indexes, and it is helpful for the effective development of gas field. Based on the principle of mass conservation, this paper defined pseudopressure function and threshold pressure gradient of two-phase flowof both gas and water, and deduced trinomial productivity equation of gas and water two-phase flowin lowpermeability gas reservoirs in considering threshold pressure gradient and formation damage effects. This paper expounded the method of calculating the trinomial deliverability equation. Through the analysis of actual case, the relation curves of the well that gas and water
two-phase flowunder the influence of threshold pressure gradient and the water/gas quality ratio in low-permeability gas reservoirs was obtained. The research shows that with the increase of threshold pressure gradient and water/gas quality ratio, the AOF becomes small. So it provides a theory basis for gas and water two-phase flow well productivity anddynamic analysis of the well in the existence of edge water, bottomwater and interlayer water in low-permeability gas reservoirs.