The movable water existent in the strata will assemble at the bottom of gas well in the producing process, which causes the water-gas ratio rising. It will affect the output and deliverability of gas well seriously, and affect the reserve assessment and the implementation of development program. Based on the pseudosteady state flow deliverability equation, the relationship between relative permeability curves and water-gas ratio in production and the equivalent skin coefficient are applied tomodify the deliverability equation under different water-gas ratio in production, and then a new deliverability equation for gas well is obtained. The practical application shows that the modified deliverability equation is more applicable for the actual production.