A channel state information (CSI) feedback method and device are disclosed. In the method, a terminal determines an orthogonal beam group and pre-coding matrix information according to codebook parameter information, where a same beam in the orthogonal beam group has same specified coefficients in first and second polarization directions, each of the specified coefficients comprises an amplitude coefficient and/or a phase coefficient; the pre-coding matrix information includes the specified coefficients and adjustment factors, and the adjustment factors are used together with the specified coefficients to determine linear combination coefficients except the specified coefficients in a linear combination coefficient set; and the pre-coding matrix information is sent to a network-side device.