The deformation of rock mass and the spatial effect of stress of a doubletrack railway tunnel in weak rock mass are analyzed by means of numerical simulation, and the calculation results are compared with the monitoring data, so as to investigate into the influence of construction on the deformation of rock mass and the spatial effect of stress. Conclusions drawn are as follows: 1) The maximum presettlement of the crown takes 53.3% of the total settlement, and the maximum preconvergence takes 67.28% of the total convergence. 2) The excavation of the top heading and the bench has great influence on the variation of the stress at the crown and the spring line. 3) The excavation of the top heading and the bench has great influence on the variation of the stress between the footlocking jet grouting piles and the rock mass, and the bench soil to be excavated has bracing effect on the tunnel contour and has some influence on the contact pressure.