The embodiments of the present application relate to the field of wireless communication technology, and provide a channel state information (CSI) feedback method and device to reduce CSI feedback overhead. In the method, a terminal determines an orthogonal beam group and pre-coding matrix information according to codebook parameter information, wherein specified coefficients of the same beam in the orthogonal beam group in a first polarization direction and a second polarization direction are the same, and the specified coefficients comprise an amplitude coefficient and/or a phase coefficient; the pre-coding matrix information comprises the specified coefficients and an adjustment factor, and the adjustment factor is used together with the specified coefficients to determine a linear combination coefficient other than a specified combination coefficient in a linear combination coefficient set; and the determined pre-coding matrix information is sent to a network-side device. In the foregoing manner, the terminal reports the specified coefficients (equivalent to partial linear combination coefficients) in the linear combination coefficient set. Since the number of reported coefficients is reduced, system overhead caused by feedback CSI information may be reduced.