Abstract: Affected by complex geological conditions, karst tunnels are prone to suffer sudden water inrush disasters during construction.To accurately assess the risk level of water inrush in karst tunnels, the structural equation model(SEM)was combined with the improved fuzzy comprehensive evaluation method(FCEM)to construct a risk assessment model for water inrush in karst tunnels.In-depth research was conducted from 6 aspects: topography, meteorological hydrology, stratigraphic factors, geological structures, karst hydrogeology, and construction factors.SEM was used to determine the standardized path coefficients of each indicator and obtain their weights, and the improved FCEM method was used to determine the risk level of water inrush in karst tunnels.Taking the Kuncheng Tunnel of the Central Yunnan Water Diversion Project as an example, the validity of the model was verified by Crystal Ball.The results showed that the Kuncheng Tunnel was within the score range of 52 to 73(level Ⅲ risk)with a probability of 90%,which was consistent with the actual situation on site.It showed that the risk assessment model of water inrush in karst tunnels based on the SEM-improved FCEM method had certain applicability.Karst hydrogeology, geological structure, and meteorological hydrology were the main influencing factors of the tunnels.Monitoring and measurement of these aspects should be strengthened during construction to avoid water inrush disasters.The research results can provide a reference for similar karst tunnel projects.