Abstract: Besides the depth and width of notching, the phase properties of notch filter also affect the SINR of correlation output to the narrow band interference suppression in DSSS. In response to this problem, it is proposed that the narrow band interference passes directly through IIR notch filter and the closed solution of output SINR improvement of correlation could be derived. The narrow band interference suppression performance is compared with those of Kwan-Martin notch filter and optimal Wiener FIR filters. A useful reference to the design and selection of filters to the narrow band suppression in DSSS is provided.