The corrected initial lining permeability coefficient is adopted to characterize the permeability of composite lining. A seepage model of composite lining is established and the correction formula of the permeability coefficient of composite lining is derived. Then， the proposed formula is verified by using the model reduced and numerical method. It is found that： when the rock surrounding permeability coefficient in the range of 1×10^-7??1×10^-6 m·s^-1， with a consideration of drainage pipes， geotextile and waterproof sheet， the effect of the permeability coefficient of composite lining on water inflow and external water pressure should not be ignored； the permeability coefficient of composite lining is closely related to the distance between two circular drainage pipes， the permeability coefficient of initial lining， the inner and outer radius of initial lining， the thickness and the permeability coefficient of geotextile； the larger the distance between two circular drainage pipes， the smaller the permeability coefficient of composite lining.