The invention discloses an NAL (network abstraction layer) module of a video codec, and the NAL module provided by the invention comprises a data selection function block, a code stream splicing function block, a split function block, an insert function block and a code stream combination function block, wherein the data selection function block is used for controlling data output; the code stream splicing function block is used for splicing the code streams output by the data selection function block; the split function block is used for splitting the code streams output by the code stream splicing function block; the insert function block is used for judging whether to insert bytes and carry out processing according to the judging result; and the code stream combination function block is used for splicing the results output by the insert function block. According to the invention, the efficiency of hardware design can be improved.