A method for reporting channel state information CSI, comprising: receiving a first reference signal set from a base station, wherein the first reference signal set comprises at least two reference signals; sending first CSI to the base station, wherein the first CSI is determined according to the first reference signal set, and the first CSI comprises a first precoding matrix indicator PMI; receiving a second reference signal set from the base station, wherein the second reference signal set is determined based on the first PMI comprised in the first CSI and a preset quantity of layers of a precoding matrix, and the second reference signal set comprises at least one reference signal; and sending second CSI to the base station, wherein the second CSI is determined according to the second reference signal set. characterised in that the sending second CSI, comprises: determining a second precoding matrix from a second codebook according to the second reference signal set; and sending the second CSI to the base station, wherein the second CSI comprises a second RI and/or a second PMI, and the second PMI is used to indicate the second precoding matrix, wherein the second codebook comprises at least one precoding matrix W, and the precoding matrix W has a structure determined according to the following equation: W = 2 NM − 1 2 w ⊗ v e jφ w ⊗ v or W ⁢ = 4 NM − 1 2 w ⊗ v w ⊗ v e jφ w ⊗ v − e jφ w ⊗ v, wherein w = [1 e jφ ··· e j ( N-1) φ] T, v = [1 e jθ ··· e j ( M -1) θ] T, [] T denotes a matrix transpose, ⊗ denotes a Kronecker product, M and N are positive integers, and θ, φ, and φ are phases, wherein the phase θ = mπ /16, and m = 0,...,15; or the phase φ = nπ /32, and n = 0,...,31; or the phase φ = lπ /2, and l =0,..,3 or l = 0,1. receiving a first reference signal set from a base station, wherein the first reference signal set comprises at least two reference signals; sending first CSI to the base station, wherein the first CSI is determined according to the first reference signal set, and the first CSI comprises a first precoding matrix indicator PMI; receiving a second reference signal set from the base station, wherein the second reference signal set is determined based on the first PMI comprised in the first CSI and a preset quantity of layers of a precoding matrix, and the second reference signal set comprises at least one reference signal; and sending second CSI to the base station, wherein the second CSI is determined according to the second reference signal set. characterised in that the sending second CSI, comprises: determining a second precoding matrix from a second codebook according to the second reference signal set; and sending the second CSI to the base station, wherein the second CSI comprises a second RI and/or a second PMI, and the second PMI is used to indicate the second precoding matrix, wherein determining a second precoding matrix from a second codebook according to the second reference signal set; and sending the second CSI to the base station, wherein the second CSI comprises a second RI and/or a second PMI, and the second PMI is used to indicate the second precoding matrix, wherein the second codebook comprises at least one precoding matrix W, and the precoding matrix W has a structure determined according to the following equation: W = 2 NM − 1 2 w ⊗ v e jφ w ⊗ v or W ⁢ = 4 NM − 1 2 w ⊗ v w ⊗ v e jφ w ⊗ v − e jφ w ⊗ v, wherein w = [1 e jφ ··· e j ( N-1) φ] T, v = [1 e jθ ··· e j ( M -1) θ] T, [] T denotes a matrix transpose, ⊗ denotes a Kronecker product, M and N are positive integers, and θ, φ, and φ are phases, wherein the phase θ = mπ /16, and m = 0,...,15; or the phase φ = nπ /32, and n = 0,...,31; or the phase φ = lπ /2, and l =0,..,3 or l = 0,1.