In shield tunnel construction, the problems that the sealing gasket of shield tunnel joints not sticking well, being wet, and not being painted with lubricant are common. As a result, a numerical calculation method for waterproof capacity of the sealing gasket is constructed. The calculation results of the model are compared with conventional calculation results, and the waterproof capacity of the sealing gasket under the conditions such as the bottom of gasket being pasted to the notch of segment, the top of gasket being painted with lubricant, and being wet is studied. The results show that: (1) The difference of closed compression force and average contact stress between the calculation results with and without consideration of the working conditions of gasket surface are 4.2% and 8.1%, respectively, which indicates that it is necessary to evaluate the waterproof capacity of the sealing gasket with consideration of gasket surface condition. (2) The lateral deformation at the bottom of liner is constrained by sticking effect, hence, both closed compression force and the average contact stress are larger than those without consideration of bottom sticking effect, and the influencing ranges are 3.1%~19.9% and 0~24.5% respectively. (3) By painting the top of gasket with lubricant, the closed compression force can be reduced and the average contact stress can be increased, and the influencing ranges are 4.7%~19.9% and 6.5%~11.1%, respectively. (4) If the sealing gaskets are wet, the closed compression force and the average contact stress will be reduced by 29.1% and 8.7%, respectively. (5) Under longterm working condition, the average contact stress of the gasket decreases due to the contact state variation of sealing gasket surface, which is decreased by 23.9% at last.