Abstract: In order to study the fracture form of surrounding rock of straight-walled vault tunnel under different burial depths, the numerical simulation tests are carried out by RFPA software.The results of numerical test show that the surrounding rock of tunnel under different burial depths are firstly destroyed from the arch foot and the corner of tunnel, then the cracks spread diagonally downwards along arch feet and diagonally upward along the corners of the wall, and eventually the fracture and instability of both side walls of surrounding rock in tunnel occurred; meanwhile, due to the large load of surrounding rock in deep tunnel, the cracks also extend from the both sides of tunnel to the arch top and the bottom floor of tunnel.Through the strain data analysis of surrounding rock, it is found that the radial strain of surrounding rock is the main cause of the fracture of surrounding rock in tunnel.The numerical test results are consistent with the related physical test results, which can further enrich the research results of fracture of deep rock mass and better guide the development and application of deep underground space.