Abstract: Thresholding based on wavelet depends on the length of the signal and the level of the noise.In most cases,the variance of the noise is unknown,so it needs to be estimated.This paper proposes an iterative method to estimate the threshold based on soft-thresholding.The convergence of the iterative algorithm is proved,and an analysis of the computational time is given.Numerical experiment shows that the algorithm is competitive to the MAD method,and the computational time is much less than MAD method.