We consider the property of the n-plane linear coherent optical-processing system in term of the similarity theorem of Fourier transform and the spatial frequency scaling transform. Suppose the initial system has arbitrary {zi}n-1 with zi being the spacing between the ith and (i + l)th planes. First, we can show that the initial system is equivalent to a system with different spacing, {zoi}n-1. Thus the values of system parameters {zi}n-1 are of little importance. Moreover, in this paper, the relation between the integral kernels of two arbitrary n-planc linear coherent optical-processing systems has been considered.