Lijiachong tunnel is a shallow-buried large-span tunnel and its surrounding medium is V weak surrounding rock. There is a tower of high electric pressure through the left hole side of the tunnel area. In order to ensure the safety of the tower,and avoid the uneren settlement of tower foundation before the tunnel excavation,the surrounding rock should be carried out pre-grouting reinforcement. Tower foundation and vault settlement before and after grouting were numerically studied with FLAC3D, simulation results indicated that tower foundation and vault settlement were significantly reduced after grouting to surrounding rock,and it could effectively control the uneven settlement of tower foundation. Compared with the actual monitoring results,the surrounding rock grouting effect was better,and the measured values accord well with values of simulation. It is feasible to forecast the grouting reinforcement effect by FLAC3D simulation.