Abstract: The Bomi section of the Sichuan-Tibet Railway passes through the glacier-covered area where multiple large-scale river compounded with faults occur. The river water is abundant, leading to a tectonic high-pressure water inrush and mud outburst disaster risk source. This paper studies the flow characteristics of large-scale river and the transformation relationship between surface water and tectonic fissure water through flow measurement and analysis of precipitation, glacier melting water, river water and groundwater hydrochemistry, isotopic characteristics, and hydrogeochemical processes. The results show that the river water in Bomi glacier covered area in Tibet is mainly supplied by glacier melting water and precipitation. In rainy season, the values of δ ¹⁸O and δ D are less than those in dry season, indicating that the structure of water-supply source is different. During the dry season, the main source of replenishment is precipitation due to the low temperature, and in the rainy season the amount of glacier melting increases sharply, which becomes the main source of recharge. The discharge of rivers Guxianggou, Bitongqu and Longchongqu, which are compounded with the fault, is larger than 4×10⁴ m³/d. However, the annual flow fluctuation is less than that of the rivers in the non-fault zone. The river water could supply the fault zone water, forming shallow circulation groundwater of 5−10 a and medium and deep circulation groundwater of more than 4000 a. There is a close hydraulic connection and frequent mutual transformation between the river and bedrock weathering fissure water in the non-fault zone. The research results can provide references for the early identification of high-pressure water and mud inrush disasters in tunnels and the formulation of disaster prevention measures in the glacier-covered area of the eastern Qinghai-Tibet Plateau.