The invention is directed to a method for receiving a feedback for at least a multicast broadcast service flow transmitting to a plurality of subscriber stations. The method comprises steps of assigning a plurality of code division multiple access (CDMA) codes to a feedback corresponding to the multicast broadcast service flow and then performing an allocation process for allocating a feedback channel for the subscriber stations. Thereafter, an announcement process is performed to announce a multiple feedback condition, the CDMA codes and the feedback channel to the subscriber stations. A channel monitoring process is performed for receiving a negative-acknowledgment (NACK)-based feedback sending from one of the subscriber stations unsatisfied with the multiple feedback condition and the NACK-based feedback is in a form of one of CDMA codes corresponding to the multicast broadcast service flow and is transmitted through the feedback channel.