The tunnelsoil particle flow model of a metro tunnel on a rail transit line No. 1 in sandcobble strata is established by particle flow code 2D (PFC2D); the stress variation laws of overlying soil induced by bench method tunnel excavated are studied and numerically simulated. The study results show that: 1) During the initial excavation phase, the stress disturbance and redistribution of the overlying soil are obvious. 2) The annular excavation affects the stress distribution of the overlying soil most obviously. 3) The excavation disturbance effect on the vertical stress is stronger than that on the horizontal one. The results coincide with the actual monitoring results and can provide theoretical guidance for tunnel excavation in sandycobble strata.