Abstract: Based on structural mechanics, the different hoop forces on upper and under a tunnel are determined to simulate water pressure in the first place. The fully-sealed hydraulic loading device for horseshoe-section tunnel-model tests was manufactured, which implements non-uniform hydraulic loading successfully. A model test were carried out to investigate its mechanical characteristics. The test conclusions are consistent with those of numerical simulation for controlled safe locations, which would verify the validity of the loading simulation for water. It solves the ‘bottleneck’ problem of water pressure loading during the model test of a tunnel. Under water pressure, the moment at the invert is more than that at the arch. The moment at the invert towards interior and that at the wall-footing is outwardly. A large eccentric tensile crack appears. The invert and wall-footing are deemed as controlled safe locations of lining. The ultimate bearing capacity of two-lane tunnel lining for high-speed passenger railway is determined under water pressure. Compressive-shearing damage takes place at the wall-footing. The bending destruction appeared at the invert. The results can provide a reference for the design and construction of a tunnel subjected to high water pressure.