The present invention relates to the technical field of wireless communications. Provided arc an indication method, a base station, and a system for channel state information (CSI) feedback. The indication method comprises: the base station allocating to a user equipment (UE) a CSI feedback method (S701); by means of allocation signaling, the base station transmitting to the UE the CSI feedback method allocated, instructing the CSI feedback method to be employed by the UE when making an aperiodic CSI report (S702). The feedback method comprises: the UE receiving the allocation instruction transmitted by the base station, acquiring the CSI feedback method allocated for the UE by the base station; when the UE confirms the triggering of an aperiodic CSI report, using the CSI feedback method allocated therefor by the base station. In the present invention, the base station can perform the selection of the appropriate aperiodic CSI feedback method on the basis of the status of carrier allocation, thereby optimizing the CSI feedback mechanism, and improving system design flexibility.