Abstract: Abstract:This paper studies two common methods of estimating the parameters of the model of the disturbances serial correlation generalized differences and generalized least squares, validates by simulated calculation that the efficiency of GD estimator may be far lower than OLS estimator in all probability and that the efficiency of GLS estimator may be also lower than OLS estimator due to the error of estimating serial correlation coefficient ρ, and improves the method of estimating ρ to heighten the efficiency of GLS estimator