Abstract: Based on the second order moment of the auto correlation estimator, a new detection parameter is proposed to extend the DSSS signal detection method in additive white Gaussian noise channel to multipath channel. The proposed detection method analyzes the characteristics of energy peak led by multipath channel and auto-correlation peak led by pseudo-code of signal at first; then according to these characteristics a new detection parameter called multipath factor is defined to eliminate the influence of multipath channel while using the second order moment of the autocorrelation estimator as the direct sequence spread spectrum signal detection method ; at last, combined with this new parameter and the second order moment of the autocorrelation estimator, a new detection method for direct sequence spread spectrum signal in multipath channel is get. The theoretical analysis and simulation results show that the proposed detection parameter can reflect the influence led by multipath channel effectively; when the signal to noise ratio is higher than -14dB, the detection performance of the proposed detection method apply to signal in multipath channel is closer to the signal in additive white Gaussian noise channel.