An interleaving and mapping method and a deinterleaving and demapping method for an LDPC codeword are provided. The interleaving and mapping method comprises: performing first bit interleaving on a parity bits part of the LDPC codeword to obtain interleaved parity bits; splicing an information bit part of the codeword and the interleaved parity bits into a codeword after the first bit interleaving; dividing the codeword after the first bit interleaving into multiple consecutive bit subblocks in a predetermined length, and changing the order of the bit subblocks according to a corresponding permutation order (bit-swapping pattern) to form a codeword after second bit interleaving; dividing the codeword after the second bit interleaving into two parts, and writing the two parts into storage space in a column order respectively and reading the two parts from the storage space in a row order respectively to obtain a codeword after third bit interleaving.