This application discloses a precoding method and apparatus, and an information transmission method and apparatus, and relates to the field of communications technologies, to help improve overall performance of a plurality of data streams corresponding to a same codeword. The precoding method includes: decomposing a channel matrix into a product of a matrix Q, a matrix R, and a matrix PH, where the matrix PH is a conjugate transpose matrix of a matrix P, both the matrix Q and the matrix P are unitary matrices, and the matrix R is an upper triangular matrix; and precoding to-be-sent data based on the matrix P.