Abstract: A deformation joint is meant to solve the problem of structural damage induced by differential settle? ment or concrete shrinkage, but it can make it difficult to achieve a watertight tunnel. Despite the use of deformation joints, there is still a lack of quantitative analysis regarding the spacing of deformation joints. Based on the actual geological conditions and structural forms of the Gongbei tunnel on the Hongkong-Zhuhai-Macao throughfare, proper spacing of deformation joints is analyzed quantitatively by simulation. The results show that: 1) if the reinforcement effect of the pipe roof under the tunnel base is not considered，it can not meet the safety requirements for the structure, even at a deformation joint space of 22 m; 2) if the reinforcement effect of the pipe roof under the tunnel base is considered, a deformation joint space of 88 m is feasible; and 3) if the reinforcement effect of the pipe roof around the tunnel is considered, the deformation joint can be canceled for the bored section from the view of the horizontal stress and vertical displacement. A deformation joint space of no more than 88 m is feasible for the bored section of the Gongbei tunnel for the sake of safety, economy and convenience considering the differential settlement that may occur at the foundation after tunnel operation.