Void between road tunnel liner and surrounding rock is one of the most frequent defects in tunnel engineering. In this paper, contact method is introduced into the numerical model to simulate the interaction between tunnel liner and surrounding rock. The relationship between the key parameters of void and safety factor of the structure is systematically studied with the numerical model. Results show that position and width of void are the key parameters, while depth and shape of void are unimportant and negligible. It can also be concluded that the decrease rate of safety factor to the increase of circular width is almost the same while void is in different position. Conclusions gained are helpful for inspection, operation status assessment and rehabilitation of road tunnel in future.