The invention discloses an interleaving and mapping method and a de-interleaving and de-mapping method of an LDPC code. The interleaving and mapping method includes the steps that: a check part in the LDPC code is bit-interleaved for the first time to obtain a check bit stream; an information bit part in the LDPC code is assembled with the check bit stream to form a first bit-interleaved LDPC code; the first bit-interleaved LDPC code is divided into a plurality of contiguous bit sub-blocks according to a predetermined length, and the sequence of the bit sub-blocks is changed according to a corresponding bit swap pattern to form an LDPC code bit-interleaved for the second time; the second bit-interleaved LDPC code is divided into two parts which are written in a column order and read out in a row order to obtain an LDPC code bit-interleaved for the third time; the third bit-interleaved LDPC code is subjected to constellation mapping according to a constellation diagram to obtain a symbol stream. The interleaving and mapping method and the de-interleaving and de-mapping method can be chosen for the different LDPC code tables, thereby better improving the system performance.