A channel coding/decoding method and an apparatus thereof in a communications system using an LDPC code reducing the different block length are provided to maintain effective reception range by using information of the LDPC. A receiver estimates a punch/reduction pattern from the received signal(1101). The receiver determines the presence of hole or the shortened bit(1103). In the receiving device is the decision procedure, it determines not to exist of hole or the shortened bit. The receiver performs the decoding process(1109). The hole/reduction pattern is delivered to the receiving device to an LDPC encoder(1105). The LDPC decoder sets up the punched bit as the disappearance. The receiving device performs the decoding process.