A Channel State Information CSI feedback method, comprising: determining first Pre-coding Matrix Indicator PMI information by a User Equipment UE, and feeding, by the UE, the first PMI information back to a network side device, wherein determining the first PMI information by the UE comprises: determining, by the UE, first channel information based on the first downlink channel measurement pilot configured by the network side device; determining second channel information by the UE, and determining, by the UE based on second PMI information, a beamforming vector corresponding to the second PMI information from a local beamforming vector codebook of the UE, wherein a dimension represented by the second channel information is different from a dimension represented by the first channel information; determining, by the UE, a beamforming vector achieving an optimal beamforming performance from the local beamforming vector codebook based on the second channel information, the beamforming vector corresponding to the second PMI information and a code stream number supported by the UE; using, by the UE, a PMI corresponding to the beamforming vector achieving the optimal beamforming performance as the first PMI information, wherein a dimension represented by the first PMI information is different from a dimension represented by the second PMI information, the first downlink channel measurement pilot is a two-dimension joint antenna array Channel State Information-Reference Signal, CSI-RS, resource, the code stream number supported by the UE is measured by the UE based on the first downlink channel measurement pilot. determining first Pre-coding Matrix Indicator PMI information by a User Equipment UE, and feeding, by the UE, the first PMI information back to a network side device, wherein determining the first PMI information by the UE comprises: determining, by the UE, first channel information based on the first downlink channel measurement pilot configured by the network side device; determining second channel information by the UE, and determining, by the UE based on second PMI information, a beamforming vector corresponding to the second PMI information from a local beamforming vector codebook of the UE, wherein a dimension represented by the second channel information is different from a dimension represented by the first channel information; determining, by the UE, a beamforming vector achieving an optimal beamforming performance from the local beamforming vector codebook based on the second channel information, the beamforming vector corresponding to the second PMI information and a code stream number supported by the UE; using, by the UE, a PMI corresponding to the beamforming vector achieving the optimal beamforming performance as the first PMI information, wherein a dimension represented by the first PMI information is different from a dimension represented by the second PMI information, the first downlink channel measurement pilot is a two-dimension joint antenna array Channel State Information-Reference Signal, CSI-RS, resource, the code stream number supported by the UE is measured by the UE based on the first downlink channel measurement pilot. determining, by the UE, first channel information based on the first downlink channel measurement pilot configured by the network side device; determining second channel information by the UE, and determining, by the UE based on second PMI information, a beamforming vector corresponding to the second PMI information from a local beamforming vector codebook of the UE, wherein a dimension represented by the second channel information is different from a dimension represented by the first channel information; determining, by the UE, a beamforming vector achieving an optimal beamforming performance from the local beamforming vector codebook based on the second channel information, the beamforming vector corresponding to the second PMI information and a code stream number supported by the UE; using, by the UE, a PMI corresponding to the beamforming vector achieving the optimal beamforming performance as the first PMI information, wherein a dimension represented by the first PMI information is different from a dimension represented by the second PMI information, the first downlink channel measurement pilot is a two-dimension joint antenna array Channel State Information-Reference Signal, CSI-RS, resource, the code stream number supported by the UE is measured by the UE based on the first downlink channel measurement pilot.