The present disclosure provides a demodulation method and apparatus, a decoding method and apparatus and a baseband chip in a communication system. The decoding method includes: when demodulated data in a buffer space is enough to form a second predetermined number of CB data, reading the demodulated data to form the second predetermined number of CB data from the buffer space; decoding the second predetermined number of CB data. The buffer space includes a plurality of buffer regions corresponding to different CWs. Each of buffer regions store the demodulated data belonging to the CW, reading the demodulated data to form the second predetermined number of CB data in the buffer space includes reading the demodulated data belonging to the CW in the buffer region corresponding to the CW. The present disclosure saves memory space of the baseband chip.