Abstract: In this paper, a new semi blind signal preprocessing algorithm (second-order cyclostationary BSS algorithm pPSoCBSS-pre-processing) is proposed. The algorithm is used to pre process the signal, so that the source signal has a controlled cycle stable characteristic, and the signal is effectively separated at the receiving end. Love method based on the transmitter source signal preprocessing, channel identification and signal separation, so that the receiver can estimate the channel mixing matrix accurately, and has excellent anti noise characteristics, this method even in underdetermined condition also can be identified and the channel performance is not lost. At the same time, measured through the computer simulation of the separation matrix estimation effect with the PI index, and compared with the JADE algorithm and SOBI algorithm, the simulation results show that the algorithm has better performance than the PI index of two kinds of traditional algorithm.