The present invention relates to communication technologies, and provides a decompression method for communication network, in which such fields as an SN are compressed by using an ROHC scheme, so that the compression efficiency is increased. The ROHC uses a WLSB algorithm to compress some fields which change regularly, and decodes by using the decompressor's context through transmitting the low significant bits in these fields. In order to avoid using the inefficient ergodic method and the incorrect direct replacing method in low bits, the present invention selects, based on the mathematical characteristics of the definition of interpretation intervals, to decode by using the method that the low bits is determined by the received k significant bits while the high bits is determined jointly by the local storage information and these k significant bits. Its decoding method can be used for decompression of an SN, a TS and an IP-ID in an ROHC compression.