The application provides a construction method and a device of a quasi-cyclic
low density parity check (LDPC) code, belonging to the technical field of communications. The construction method comprises the following steps of: acquiring a complete cyclic difference set D={d1, d2, ..., dk}, wherein
lambda of D is equal to 1, modulus v=k2-k+1, and
lambda represents the number of two-tuples (di, dj) satisfying the formula di-dj=a in D, lis less than or equal to i, j is less than or equal to k, i is not equal to j, a is not equal to 0 (modv) and k is an even number; constructing an M*N
shift matrix S(H) by using the D, wherein each position in S(H) is two-tuples (di, dj) selected from the D; and replacing the two-tuples (di, dj) at each position in M*N S(H) with a corresponding cyclic matrix Wm, n with weight being 2 and constructing a
parity check matrix H of MP*NP, wherein Wm, n=I(di) + I(dj), the I(di) represents a cyclic
permutation matrix obtained after a P*P unit matrix is shifted rightwards for di positions cyclically and P is equal to v. Under the same condition, the construction method can improve the performance of the LDPC code, is provided with a low
error floor and has high coding convergence speed.