A method for providing feedback of Channel State Information, CSI, comprising: obtaining, by a terminal, a first pre-coding matrix set for a first sub-band corresponding to the number of downlink transmission layers, wherein the first pre-coding matrix set comprises multiple first pre-coding matrices and each physical resource in the first sub-band corresponds to one of the multiple first pre-coding matrices in the first pre-coding matrix set; determining, by the terminal, a Channel Quality Indicator, CQI, for a second sub-band according to downlink channel information and according to the first pre-coding matrix set for the first sub-band; and providing, by the terminal, feedback of the CSI, wherein the CSI comprises: indication information of the first pre-coding matrix set for the first sub-band, and the CQI for the second sub-band; or a rank indicator, RI, indicating the number of downlink transmission layers, indication information of the first pre-coding matrix set for the first sub-band, and the CQI for the second sub-band; wherein: an i-th physical resource in the first sub-band corresponds to a k-th pre-coding matrix in the first pre-coding matrix set; and k=i mod K, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band; or k=ceil(i/v) mod K, wherein ceil(i/v) represents a minimum integer no less than i/v, v=RI, or v is the number of antenna ports, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band obtaining, by a terminal, a first pre-coding matrix set for a first sub-band corresponding to the number of downlink transmission layers, wherein the first pre-coding matrix set comprises multiple first pre-coding matrices and each physical resource in the first sub-band corresponds to one of the multiple first pre-coding matrices in the first pre-coding matrix set; determining, by the terminal, a Channel Quality Indicator, CQI, for a second sub-band according to downlink channel information and according to the first pre-coding matrix set for the first sub-band; and providing, by the terminal, feedback of the CSI, wherein the CSI comprises: indication information of the first pre-coding matrix set for the first sub-band, and the CQI for the second sub-band; or a rank indicator, RI, indicating the number of downlink transmission layers, indication information of the first pre-coding matrix set for the first sub-band, and the CQI for the second sub-band; wherein: an i-th physical resource in the first sub-band corresponds to a k-th pre-coding matrix in the first pre-coding matrix set; and k=i mod K, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band; or k=ceil(i/v) mod K, wherein ceil(i/v) represents a minimum integer no less than i/v, v=RI, or v is the number of antenna ports, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band indication information of the first pre-coding matrix set for the first sub-band, and the CQI for the second sub-band; or a rank indicator, RI, indicating the number of downlink transmission layers, indication information of the first pre-coding matrix set for the first sub-band, and the CQI for the second sub-band; wherein: an i-th physical resource in the first sub-band corresponds to a k-th pre-coding matrix in the first pre-coding matrix set; and k=i mod K, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band; or k=ceil(i/v) mod K, wherein ceil(i/v) represents a minimum integer no less than i/v, v=RI, or v is the number of antenna ports, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band an i-th physical resource in the first sub-band corresponds to a k-th pre-coding matrix in the first pre-coding matrix set; and k=i mod K, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band; or k=ceil(i/v) mod K, wherein ceil(i/v) represents a minimum integer no less than i/v, v=RI, or v is the number of antenna ports, i=0,1,2...N, k=0,1,2,3,...,K-1, K is the number of pre-coding matrices in the first pre-coding matrix set, and N is the number of physical resources in the first sub-band