The crosssection form of sealing gasket for segment joint of deep drainage shield tunnel in Shanghai with high water pressure (1.2 MPa) is designed and studied so as to meet the longterm waterproofing performance of segment joint sealing gasket under conditions of opening of 8 mm and dislocation of 10 mm. The waterproofing performance and closed compression force of sealing gaskets with different crosssection forms are numerically simulated; the sealing gasket crosssection form with optimal waterproofing and mechanical performance is obtained by comparison and optimization; and the waterproofing performance and closed compression force are tested. The test results show that the sealing gasket with recommended crosssection form (with Shore A Hardness of 67) can meet the requirement of longterm waterproof and requirement of segment assembling under segment joint opening of 8 mm and dislocation of 10 mm and high water pressure of 1.2 MPa.