The invention discloses a check matrix generation method which can obtain check matrices of different rates by means of the combination of decomposition and interlacing of a basic check matrix for defining mother codes. The invention also discloses a low density parity check code coding method, a check matrix generator and a coder for the check matrix generation method. The check matrix generation method extends the basic check matrix by means of decomposition, reduces the rate while meeting the check relationship required for higher rate, and avoids the complexity in check structure during shortening and deletion. Additionally, the combination of decomposition and interlacing can flexibly adjust the degree distribution of the check nodes, reduce the performance loss of the extension method under the condition of low rate, and greatly reduce the frame error rate or the block error rate in the actual communication system.