Abstract: An auto/cross covariance approach for parameter estimation of the discrete linear transfer function model is a new method.The daily rainfall and runoff data series on four catchments are chosen to examine the new method(4 years rainfall and runoff data series for calibration periods and 2 years for the verification periods).The comparison between the results from the new method and coven. licnal ordinary least squares method shows that the accuracy of the new method is better than those of the conventional least squares method and the latter is a special case of the former.