A channel state information, CSI, feedback method, comprising: determining, by a terminal, precoding matrix indication information, PMI, wherein: the PMI comprises: first base vector information associated with first base vectors; second base vector information associated with second base vectors; and second coefficient information, used to derive first coefficients and second coefficients, the second coefficient information comprising second coefficient amplitude information and second coefficient phase information; a CSI feedback band comprises a plurality of frequency domain units, each frequency domain unit having a plurality of frequency domain resources; frequency domain resources in each of the plurality of frequency domain units of a same transmission layer correspond to a same precoding vector, each precoding vector being a linear combination of the first base vectors with weighting coefficients being the first coefficients; and the first coefficients corresponding to a same first base vector define a first coefficient vector, the first coefficient vector being a linear combination of the second base vectors with weighting coefficients being the second coefficients; and feeding back, by the terminal, CSI containing the PMI to a base station, characterized in that the second coefficient amplitude information comprises: two components quantized to be between 0 and 1 to generate two quantized components, wherein a coefficient amplitude used in the precoding vector is a product of the two quantized components and the two components comprise a first amplitude component and a second amplitude component. first base vector information associated with first base vectors; second base vector information associated with second base vectors; and second coefficient information, used to derive first coefficients and second coefficients, the second coefficient information comprising second coefficient amplitude information and second coefficient phase information; a CSI feedback band comprises a plurality of frequency domain units, each frequency domain unit having a plurality of frequency domain resources; frequency domain resources in each of the plurality of frequency domain units of a same transmission layer correspond to a same precoding vector, each precoding vector being a linear combination of the first base vectors with weighting coefficients being the first coefficients; and the first coefficients corresponding to a same first base vector define a first coefficient vector, the first coefficient vector being a linear combination of the second base vectors with weighting coefficients being the second coefficients; and feeding back, by the terminal, CSI containing the PMI to a base station, characterized in that the second coefficient amplitude information comprises: two components quantized to be between 0 and 1 to generate two quantized components, wherein a coefficient amplitude used in the precoding vector is a product of the two quantized components and the two components comprise a first amplitude component and a second amplitude component. two components quantized to be between 0 and 1 to generate two quantized components, wherein a coefficient amplitude used in the precoding vector is a product of the two quantized components and the two components comprise a first amplitude component and a second amplitude component.