Abstract: External hydraulic pressure upon tunnel lining is one of important factors of design lining in tunnel engineering.How to calculate external hydraulic pressure upon tunnel lining is an urgent problem.The previous relevant researches may be divided into the followings: reduction coefficient method,theory analysis method,analytical-numerical method,hydrogeochemical method,seepage field analysis method,and so on.The coupled analysis model of uniform seepage flow force and stress field is set up,and the model considers that the permeability coefficient varies with stress level.