Abstract:This paper proposes a method for narrowband interference suppression in Direct Sequence Spread System(DS-SS). The distribution of the transform domain data is analysed, and it is approximated by Gaussian distribution. The variance of Gaussian distribution is the sum of the variance of the spread spectrum signal and the variance of the noise, so if it; is estimated, it can be used as the threshold in designing the interference suppression filter. Maximum Likelihood (ML) technique is used for estimating the variance to achieve the auto-matic threshold setup. Theoretical analysis and simulation show that this method has good performance in suppressing the narrowband interference in DS-SS.