A Channel State Information, CSI, feedback method, comprising: determining a first precoding matrix W 1 in a set of first precoding matrices, and determining a first precoding matrix index value corresponding to the first precoding matrix W 1, the first precoding matrix W 1 consisting of beam groups for a plurality of antenna groups of an antenna array; determining a second precoding matrix W 2 in a set of second precoding matrices, and determining a second precoding matrix index value corresponding to the second precoding matrix W 2, the second precoding matrix W 2 comprising a beam selection section for selecting beams from the beam groups for each antenna group and a phase adjustment section for adjusting phases among the plurality of antenna groups; and feeding back the first precoding matrix index value and the second precoding matrix index value to an access device, to obtain a precoding matrix W for data transmission, the CSI feedback method being characterized in that: the precoding matrix W is calculated using the following equation: W = W 1 W 2 = X 0 0 X 1 X 2 ⋱ 0 X M − 1 ⋅ W 2; the first precoding matrix W 1 is a block diagonal matrix comprising elements of 0 other than diagonal blocks where a beam group matrix X i is located, i = 0,1,···,M -1, M represents the quantity of the antenna groups for the antenna array, X i represents a beam group for an i th antenna group and it is a N i × L i matrix with each column representing one beam direction, N i represents the quantity of antenna elements in the i th antenna group, N represents a total quantity of antenna elements for the antenna array and N = ∑ i = 0 M − 1 N i, and L i represents the quantity of beams in the beam group for the i th antenna group; the second precoding matrix W 2 is used for beam selection and phase adjustment, and it is capable of selecting several beams from each beam group and adjusting phases among the selected beams for each antenna group, to acquire a final precoding matrix; and the second precoding matrix W 2 is a ∑ i = 0 M − 1 L i × r matrix, where r represents a rank of the precoding matrix W. determining a first precoding matrix W 1 in a set of first precoding matrices, and determining a first precoding matrix index value corresponding to the first precoding matrix W 1, the first precoding matrix W 1 consisting of beam groups for a plurality of antenna groups of an antenna array; determining a second precoding matrix W 2 in a set of second precoding matrices, and determining a second precoding matrix index value corresponding to the second precoding matrix W 2, the second precoding matrix W 2 comprising a beam selection section for selecting beams from the beam groups for each antenna group and a phase adjustment section for adjusting phases among the plurality of antenna groups; and feeding back the first precoding matrix index value and the second precoding matrix index value to an access device, to obtain a precoding matrix W for data transmission, the CSI feedback method being characterized in that: the precoding matrix W is calculated using the following equation: W = W 1 W 2 = X 0 0 X 1 X 2 ⋱ 0 X M − 1 ⋅ W 2; the precoding matrix W is calculated using the following equation: W = W 1 W 2 = X 0 0 X 1 X 2 ⋱ 0 X M − 1 ⋅ W 2; the first precoding matrix W 1 is a block diagonal matrix comprising elements of 0 other than diagonal blocks where a beam group matrix X i is located, i = 0,1,···,M -1, M represents the quantity of the antenna groups for the antenna array, X i represents a beam group for an i th antenna group and it is a N i × L i matrix with each column representing one beam direction, N i represents the quantity of antenna elements in the i th antenna group, N represents a total quantity of antenna elements for the antenna array and N = ∑ i = 0 M − 1 N i, and L i represents the quantity of beams in the beam group for the i th antenna group; the second precoding matrix W 2 is used for beam selection and phase adjustment, and it is capable of selecting several beams from each beam group and adjusting phases among the selected beams for each antenna group, to acquire a final precoding matrix; and the second precoding matrix W 2 is a ∑ i = 0 M − 1 L i × r matrix, where r represents a rank of the precoding matrix W.