A decompression method for communication network is provided, in which domain SN is compressed by ROHC, so the compression efficiency is increased. The WLSB algorithm is used to compress some domains which change regularly, decoding is processed by transmitting low significant bit in these domains and the context of the decompression party. In order to avoid using inefficient ergodic method and incorrect direct replacing method in low bit, that using low bit is determined by k significant bit received, the method which is determined by local storage information and k significant bit together is used for decoding in high bit, according to mathematic feature in the definition of interpretation intervals. The decoding method can be used in decompression for SN, TS and IP-ID in ROHC compression.