The study on influencing factors on mechanical properties of ethylene-propylene-diene monomer(EPDM) sealing gasket of segment joint of shield tunnel is of great significance. Hence, a testing system is developed, and the feasibility of the system is verified by case study. And then the 6-factor-and-3-level sensitivity analysis is carried out on influencing factors of mechanical properties of sealing gasket, such as cross-section parameters of sealing gasket(hole shape, groove number and holing rate), hardness of sealing gasket material and assembly posture of sealing gasket (opening and dislocation amount), by numerical model and orthogonal analysis method. Finally, the closed compressive force and contact stress distribution of sealing gasket are regarded as analytical indices considering the requirement of mechanical properties and waterproofing properties of sealing gasket. The results show that: (1) The influencing degree of joint opening amount on the closed compressive force is the greatest, followed by those of cross-section holing rate, rubber hardness, grooving number, hole shape and other factors, and that of dislocation amount is the smallest. (2) The influencing degree of hole shape on contact stress distribution is the greatest, followed by those of cross-section holing rate, dislocation amount, other factors, opening amount and rubber hardness, and that of the grooving number is the smallest. Single factor analysis is carried out on factors that affecting the mechanical properties of sealing gasket greatly to provide optimization scheme for sealing gasket based on analytical results and water-proof property prediction method.