Abstract: In view of the influence of seasonal water level change on the tunnel constructed by mining method adjacent to river, based on the section works where the underground tunnel of Ji’nan Rail Transit Line R3 under-passes the east branch ditch of Daxin River, a three-dimensional numerical model is established by using finite difference software FLAC3D to analyze the construction response and mutual feed effect of the underground-excavated tunnel under-passing main channel with the change of water level. Research shows that when adopting advance pipe-roof+full section grouting+channel both-side grouting reinforcement, the maximum compressive stress of the lining is reduced by 55.7% and 41.3% respectively compared with the other two schemes, and the maximum tensile stress of the lining is reduced by 55.9% and 33.7% respectively. Moreover, the stress and deformation of stratum and channel are superior to those of the other two schemes, which are within the allowable range of deformation control standard value. Engineering practice has proven that for construction of river-adjacent underground-excavated tunnel under-passing channel in high-flow season, adopting combined reinforcement scheme of advance pipe-roof+full section grouting+channel both-side grouting can effectively control stratum deformation and ensure tunnel construction safety.