In the process of enhanced of development of gas wells, the liquid loading may cause obstacles for the affective production of the gas wells. Gas-foam drainage technology has the advantage of low cost and simple operation. The design of the drainage technology requires providing a reliable formula to evaluate the friction coefficient of foam in the tube. In this paper, we have applied a theoretical analysis and indoor experiments to study the liquid volume lifted by the gas-foam flow and the pressure gradient in the well pipe in the process of foaming drainage, and established the calculating formula for the foaming friction in the well pipe, considering the different injection speed of the foaming agent. The validation for comprehensive analysis of the foaming technology in production gas wells.