Abstract: This paper proposes a semi-distributed scheduling algorithm to decrease the feedback of Channel State Information. According to the probability of feedback interruption and total number of users, the threshold of channel state information feedback is set up respectively at base station and relay. In every slot, through the comparison with the threshold, users decide whether to feedback the corresponding link information about the signal to noise ratio. The base station, according to the feedback from users, decide which transmission modes will be selected. In addition, this paper gives detailed theoretical derivation on performance index of the proposed algorithm, such as the number of feedback users and the average achievable rates etc. Moreover, under the AF protocol, the fianl result shows the performance of system by using this scheme is corresponding to mathematical derivation. Furthermore, the proposed algorithm could greatly reduce (over 90%) the quantity of feedback information in the system.