This research presents the time series analysis on the Keelung river basin. univariate ARMA model and multivariate ARMAX model were applied for the analysis and forecast of the river level in Dar-Ji bridge. Two upstream additional gauging stations at Wu-Du bridge and Song-San bridge were added for the study of the ARMAX model. The simulation results show that the analysis and the multi-steps ahead forecasting of Dar-Ji bridge by the ARMAX model is much better than the ARMA model.