The stress of surrounding rock is analyzed with FLAC^3D when tunnel excavation approaches the geological interface. The influencing factors are also studied in this paper. The results show that there will be stress concentration in surrounding rock ahead the excavating face when excavation is from hard rock to soft rock or from soft rock to hard rock.  The radial stress of surrounding rock of side wall ahead the excavating face will increase with increasing lateral stress, and the longitudinal stress of surrounding rock of the crown and side wall ahead the excavating face will increase with increasing longitudinal stress.