Based on the present properties of Walsh sequences,a new property of an L × L- order complete Walsh sequence set is derived,i.e.there exists sequence identity of L/4 columns of arbitrary three or four sequences.According to this property,it is deduced that the sum of binary Walsh numbers in the identical columns of four sequences is zero,and that,the mapping sequences of three superposition sequences are orthogonal to a certain number of sequences in the sequence set.Moreover,the partial correlation between the superposition sequences and the original sequences is verified by simulations and is applied to a parallel combinatory spread spectrum communication system.Finally,the soft decision for QPSK modulation of the spread spectrum system is briefly analyzed.