<FONT face=Verdana>This paper presents an algebraic method for designing circulant-shift values of permutation matrices in an array sparse parity-chick matrix which defines the QC-LDPC codes. The basic ideal is that the problem of constructing an array H-matrix by the permutation matrix can be converted into the problem of constructing a subscript matrix

and then all elements (subscript values) in this subscript matrix

i.e.

the circulant-shift values of all permutation matrices in the array H-matrix

can be computed by a well-desinged sequence expression which is a function of the row and column weight of H-matrix and the dimension of permutation matrix and can be formed by the necessary and sufficient condition of Fossorier. The H-matrix formed by this method can eliminate the cycle 4 and can form at least girth 6.