The water discharge continues unabating in the construction of Niulanjiang-Dianchi replenishment project of Tunnel 6 in Yunnan Province, witch affects the construction progress．In order to guide the next construction work，the Q-S curve method，hydro-geological analogue method and Dajing method were chosen to predict water inflow. The forecast results of three method are 25088，17580，24528 cubic meters per day respectively.By contrast，The minimum error is hydro-geological analogy method that accords with actual tunnel construction excavation.The calculation results of karst water bursting can directly guide the construction．