The invention discloses a coding
delay method for reducing double
diagonal quasi-cyclic
low density parity check code, comprising the steps: based on the set extended
code rate of 1 / k, the double
diagonal of basis matrix at the m line and n row can be extended along the direction of the double
diagonal to form an expended matrix of the double diagonal structure, wherein, k is equal to 3, 4, 5...k0, and 1 / k0 is the minimum
code rate; a first nonzero element of the i*m+1line check part is moved towards
left direction to (n-m+l) line along the i*m+1line, wherein, i is equal to 1, 2, ..., k0-1; a first check relation is taken as
initiation factor to calculate check bit of n-m+l row; by utilizing the check relation of moving towards
left direction to (n-m+l) line, a plurality of groups of check bits are calculated in parallel by a mode of recursive coding.