Based on the " Sutong GIL comprehensive pipe gallery project", the distribution of bending moment and displacement of B3 block under the vertical uniformly distributed load of the arch roof was studied by finite element software simulation. Displacement distribution coefficient and moment distribution coefficient are introduced to reveal the distribution of bending moment and displacement of B3 block under different longitudinal forces. The research reveals the corresponding relationship between longitudinal force and joints open amount and explores the distribution mechanism of bending moment and displacement. The results show that: (1) Longitudinal force can increase the distribution of bending moment and displacement of the segments, but the distribution of longitudinal force towards the internal force of the structure is nonlinear and phased, when no joint opening exist, the increase of longitudinal force can barely impact on the distribution of internal force and deformation for the segments, while when joint opening is observed, the distribution will be increased to some extent with the increase of longitudinal force. (2) The contact surface of the joint can be sufficiently contacted under the effect of longitudinal force, the main controlling factor at this time is the contact surface. The direct controlling factor is joint opening and dislocation. With the opening of circumferential joints, the internal force of the structure is transferred through the tenon structure instead of the contact surface, and as a result, the distribution capacity of the overall internal force of the structure decreases. (3) Under normal load, with the increase of vertical load, the internal force distribution capacity of the structure tends to be stable after the contact of tenon and mortise. (4) In practical engineering, when loss of longitudinal force happens, partial stress concentration of the structure will occur due to the redistribution of internal force, in consequence, particular consideration should be provided for the project.