A method for feeding back channel state information, comprising: in a transmission mode of dynamic switching between a Single-User Multiple Input Multiple Output, SU-MIMO, transmission mode and a Multiple-User Multiple Input Multiple Output, MU-MIMO, transmission mode, user equipment, UE, sending the channel state information to a network side, which comprises a Pre-coding Matrix Indicator, PMI, indicating a Pre-coding Matrix for the SU-MIMO mode and information indicating for the MU-MIMO transmission mode a transmission layer with the best channel quality among all transmission layers indicated by the Pre-coding Matrix, to indicate the network side to send data to the UE by the transmission layer with the best channel quality when the network side determines to adopt the MU-MIMO transmission mode; wherein the information indicating the transmission layer with the best channel quality includes average CQIs of different transmission layer sets and a differential CQI between a CQI of each transmission layer and an average CQI of the transmission layer set to which said each transmission layer belongs, before the step of the UE sending the channel state information to the network side, the method further comprises: dividing transmission layers into at least two transmission layer sets; obtaining the average CQI of each transmission layer set respectively; and obtaining the differential CQI between the CQI of each transmission layer and the average CQI of the transmission layer set to which said each transmission layer belongs according to the average CQI of each transmission layer set. in a transmission mode of dynamic switching between a Single-User Multiple Input Multiple Output, SU-MIMO, transmission mode and a Multiple-User Multiple Input Multiple Output, MU-MIMO, transmission mode, user equipment, UE, sending the channel state information to a network side, which comprises a Pre-coding Matrix Indicator, PMI, indicating a Pre-coding Matrix for the SU-MIMO mode and information indicating for the MU-MIMO transmission mode a transmission layer with the best channel quality among all transmission layers indicated by the Pre-coding Matrix, to indicate the network side to send data to the UE by the transmission layer with the best channel quality when the network side determines to adopt the MU-MIMO transmission mode; wherein the information indicating the transmission layer with the best channel quality includes average CQIs of different transmission layer sets and a differential CQI between a CQI of each transmission layer and an average CQI of the transmission layer set to which said each transmission layer belongs, before the step of the UE sending the channel state information to the network side, the method further comprises: dividing transmission layers into at least two transmission layer sets; obtaining the average CQI of each transmission layer set respectively; and obtaining the differential CQI between the CQI of each transmission layer and the average CQI of the transmission layer set to which said each transmission layer belongs according to the average CQI of each transmission layer set. dividing transmission layers into at least two transmission layer sets; obtaining the average CQI of each transmission layer set respectively; and obtaining the differential CQI between the CQI of each transmission layer and the average CQI of the transmission layer set to which said each transmission layer belongs according to the average CQI of each transmission layer set.