Abstract: Considering inconvenience of obtaining accurate hydrogelogical parameters when using determined model to predict the inflow of tunnel,this paper takes the groundwater system as a "black box" and establishes a time-series model to forecast the inflow in tunnel,based on analyzing and extracting the trend component,the periodic component and the stochastic component of the historical observed data.The method is applied to the Tongluoshan tunnel.The Mean Absolute Percent Error(MAPE) of the inversion series is 14.67%,while the MAPE of the prediction series is 14.34%.The results show that this model has a high prediction accuracy.