In order to study the influence of parallel pilot tunnel excavation on the main tunnel of high-ground stress soft rock tunnel, based on the long-term monitoring data and the finite difference program FLAC3D, a numerical simulation model was established to study the influence of parallel pilot tunnel excavation on the surrounding rock stress, displacement, and plastic zone distribution of the main tunnel, and the optimal spacing between the main hole and the horizontal guide is determined. The results show that during the excavation of the main tunnel when the distance between the tunnel face and the monitoring section is 3.63 times the width of the main tunnel, the vault settlement, upper horizontal convergence, middle horizontal convergence, and lower horizontal convergence of the monitoring section account for more than 80 % of the final deformation value. After the deformation of the surrounding rock is stable, the upper horizontal convergence value and the middle horizontal convergence value are greater than the vault settlement. The advanced excavation of the parallel pilot tunnel can effectively improve the mechanical environment around the main tunnel.? When the distance between the main tunnel and the parallel pilot tunnel is large, the improvement effect of the surrounding rock stress is not obvious. As the distance between the two tunnels gradually decreases, the improvement effect of the surrounding rock stress gradually increases. However, when the distance between the main tunnel and the parallel pilot tunnel is too small, the plastic zone generated by the excavation of the two tunnels will be connected. The vault settlement value and the arch bottom uplift value of the main tunnel increase with the decrease of the distance between the main tunnel and the parallel pilot tunnel, and the horizontal displacement value of the left and right arch waist decreases first and then increases with the decrease of the distance between the main tunnel and the parallel pilot tunnel. When the distance between the two tunnels decreases from 5.0D to 3.0D, the vault settlement value and the arch bottom uplift value increase from -0.598m and 0.426m to -0.679m and 0.514m respectively.