Due to the complex variability of karst areas, it has been a major problem difficult to break through in hydrogeology for how to accurately predict the water inrush of long tunnels in complex karst areas. Based on the case of the water inrush in Niulanjiang-Dianchi water diversion project, 5 major control factors: the lithological characteristics of the stratum and the influence of geological structure, the selection of the inrush water prediction method, the selection of calculation parameters, the determination of the influence range of the tunnel gushing water and the diversion of the hydrogeological unit are used respectively to summarize and analyze the impact on the prediction accuracy of water inrush in tunnels. According to the change law of the predicted value and the actual value under different factors control, a method to improve the prediction accuracy of the water inrush in tunnel is put forward, and its feasibility is verified by combining engineering examples. The conclusion can provide reference for improving the future prediction accuracy of tunnel water bursting in karst area.