Abstract: In order to determine the design parameters and corresponding construction method of the small-inter? val tunnel, the deformation and mechanical behaviors were obtained by a simulation analysis of construction of the small-interval section excavated by bench method, CD method and CRD method in the surrounding rock of grade Ⅳ by FEM software based on the construction of the small-interval section at north side of the Baiyanggou tunnel on the Xingyan expressway. The monitoring results show that it is reasonable for this section of small-interval tunnel to be constructed by bench method in the surrounding rock of grade Ⅳ and it is effective for the safe and smooth construction of the small-interval section by reinforcement of the rock pillar between the two tunnel tubes with a combination of pre-stressed long anchor bolts and advance ductule injection.