Abstract: With increase of requirements for environmental protection in recent years, the concept of "preferred blocking and limited drainage" has been put forward for the water-rich tunnels, and it′s necessary to fully consider the capability of water pressure resistance of the lining structure of water-rich mountain tunnels. Based on the Chuntianmen tunnel, it analyzes the structure of water-resistant lining under bearing of full water pressure by a "loadstructure" model, and its mechanical characteristics were obtained. The results show that the quasi-round lining structure can bear the load of external water pressure very well; the safety factor is relatively small due to full-section of lining structure being under compression, and the maximum axial force and bending moment occur at the arch spring junction with small radius, so it′s also the weakest point of the structure