It is obviously a simplification to consider the tunnel lining as uniformly permeable.In reality it is more likely that there are specific leaks assocoated with segmental lining joints. In the case of in situ concrete linings, construction joints can provide leakage paths, accounting for most of the water leakage. In this paper, based on the mechanical model of segment joint, the analytical expression of magnitude of joint opening was developed, in light of which, the occurrence of water leakage through the joint system can be judged. Taking the metro line No.1 in Shanghai as an example, effects of such parameters as joint flexural stiffness, bolt location, bolt stiffness, bolt prestress, etc. on the magninitude of the joint opening were analyzed respectively through the analytical solution. The results not only help us realize the influence mechanism of segment design on the magnitude of joint opening of the segmental linings, but also provide the guidance for waterproof design of the shield tunnel.