Abstract: Forecasting the water inflow in tunnels is of great importance to the tunnels' design and construction. This paper takes an access tunnel of hydropower station in Angola as an example and analyzes water inflow factors based on the statistics of water inrush, water temperature, water chemistry and variation of groundwater level. According to the difference of water permeability, rock mass of the fault fracture zone in tunnel was classified into 3 types. Based on the established model, the maximum water inflow was estimated using the Bernoulli equation of fluid mechanics and the normal water inflow was estimated using the formula of stable flow. The estimated result is consistent with the actual situation. The authors finally propose some engineering treatment measures for the water gushing section, and some preventive measures of layout of borehole drainage in the fractured rock mass zone with water inflow. The research can provide reference for other similar engineering problems of water gushing.