Abstract: The open TBM is characterized by safe and fast construction, but its excavation and support methods are obviously different from the drill-blasting method, and the stress characteristics of the tunnel support structure are special. Therefore, based on the flat guide project of Jiajinshan Tunnel on National Highway G351, a numerical simulation of surrounding rock pressure of open TBM tunnel considering the force of grippers is carried out, and the distribution characteristics and development law of surrounding rock pressure are analyzed. The results show that: (1) The stronger the TBM shield support, the smaller the deformation of surrounding rock is, but the greater the pressure of surrounding rock is; (2) The surrounding rock pressure increases significantly with the increase of the surrounding rock grade, and the force of grippers becomes particularly significant in grade V surrounding rock; (3) The surrounding rock pressure increases with the buried depth, while the rate of increase gradually decreases and finally the surrounding rock pressure tends to stabilize; ( 4 ) The joint surface controls the spatial distribution of the surrounding rock pressure, leading to a coincidence between the location of its sudden change and the shear failure zone, this location is orthogonal to the joint surface; (5) The surrounding rock pressure first decreases and then increases with the increase of the thrust of tunnel face. An appropriate thrust helps to reduce the surrounding rock pressure, but an excessively high thrust will increase it.