Abstract: There have been substantial research results on the material properties and structural stress state of tun? nel single-layer lining. However, limited studies have been done on the distribution characteristics of water pressure. In view of this, taking the single-layer shotcrete lining structure and composite sandwich lining structure as the research subjects, this paper deduces the water pressure calculation formula to analyze the pattern of how different factors, such as permeability coefficient of the shotcrete layer and thickness of the single-layer lining, affect the water pressure, based on the seepage continuity equation and Darcy′s law. The results show that: (1) when carrying out the design of single-layer linings, measures should be taken to reduce the permeability coefficient of the surrounding rock, such as surrounding rock grouting, and necessary drainage measures shall also be taken, without too much emphasis placed on the seepage resistance of the outer shotcrete layer, so as to reduce the water pressure of the single-layer lining structure; (2) the thickness of the single-layer lining should be minimized as much as possi? ble, with the recommended thickness not exceeding 40 cm, under the premise that it meets the role of surrounding rock load and self-weight load; (3) the inner-layer thickness of the composite sandwich structure should be less than 4/5 of the thickness of the outer layer.