The invention discloses a coding method and apparatus, a communication apparatus and a communication system. The coding method includes the steps: coding an input bit sequence by using a low density parity check LDPC matrix, wherein a base map of the LDPC matrix is represented as a matrix of m rows and n columns; m is an integer greater than or equal to 5, and n is an integer greater than or equalto 27; the base map includes at least a sub-matrix A and a sub-matrix B; the sub-matrix A is a matrix of 5 rows and 22 columns; the sub-matrix B is a matrix of 5 rows and 5 columns; and the sub-matrix B includes a column having a weight of 3 and a sub-matrix B' with a double diagonal structure. The coding method and apparatus, the communication apparatus and the communication system are capable of supporting coding requirements for various lengths of information bit sequences.