Abstract: In order to evaluate the waterproof performance of shield tunnel joints that are beyond the allowable opening amount and dislocation amount of design, and to explore the limit of sealing gasket opening amount and dislocation amount that meet the waterproof requirements, based on the shield tunnel project of Wenzhou Urban Rail Transit Line M1, a designed sealing gasket is selected for carrying out the waterproof numerical simulation under the condition of extreme opening and dislocation, then the section of the gasket is further optimized. Research results show that: the maximum assembly force required for compressing the sealing gasket is 38.6 kN/m, which meets the requirement of shield tunnel assembly force of being less than 60 kN/m; under both the working conditions of sealing opening and dislocation, the waterproof ability of sealing gasket will be weakened; but the joint waterproof performance can meet the engineering requirements by optimizing the section shape of the elastic sealing gasket.