In order to reduce the noise in signal and to increase Signal to Noise ratio, the paper introduces the principle of threshold de-noising, the soft-thresholding and hard-thresholding of estimating the wavelet coefficients. An improved de-noising method and the model of improved estimating machine are put forward by use of aiming to the inherent shortcomings of above two traditional methods. The simulation results prove that the proposed method shows good de-noising quality and can overcome inherent shortcomings of above two traditional methods to a degree.