Abstract: The engineering geology and hydrogeological conditions of the entrance section of Dongtianshan tunnel are extremely complicated. The tunnel passes through the silty clay cover layer, the holocene active seismic fault F1 and the highly weathered water-rich tuff sandstone successively. Due to water-sealing of the silty clay cover layer,local water resistance at the F1 fault and water supply from the melted permafrost snow of Mount Tianshan, the highly weathered tuff sandstone has formed a wide range of water storage structure, leading to great risks and challenges in the construction of left and right entrance sections of the tunnel. In this paper, a comprehensive geological prediction method combining geological record-geophysical exploration-drilling is adopted, the spatial relationship and genesis of the fault and confined weathered fissure water are clarified, as well as the water inflow during tunnel excavation is predicted combined with field water inflow survey and a series of technical means, which ensures safe and smooth construction of the tunnel.