Abstract: This paper presents a theoretical analysis in the sense of the Neyman-Pearson (N-P) test about the relationship between fusion rule and local decision rules in the parallel distributed detection fusion system with multiple sensors. It combines wavelet filter based on soft-threshold with the parallel distributed detection fusion system with multiple sensors ideally, and derives the determination of decision rules of two sub-optimal systems and globally optimal system completely. The detection performances of three systems above are computed numerically for the problem of detecting a known signal embeded in Rayleigh noise. The results obtained indicate that the presented method can enhance the radar detection performance remarkably.