In asynchronous V-BLAST over the nonselective Rayleigh fading channel, the performance of the existing linear detection algorithms improve slowly as the SNR increasing. Meanwhile, the performance of traditional iterative parallel interference cancellation (PIC) algorithm is depressed by the error propagation in the iteration process. In this paper, an iterative PIC algorithm based on pre-processing matrix is proposed: the transmitted signal is spread by pre-processing matrix in transmitter to achieve the space-time diversity gain, and low complexity iterative PIC algorithm is used in receiver, which relieves the error propagation by the pre-processing matrix. The performance improvement is verified by simulation. Under the condition of 8 transmit antennas and 4 receive antennas at the BER of 10−3, about 7dB gain is offered by proposed algorithm compared with traditional algorithm.