A channel state information CSI receiving method, comprising: receiving, by a network device, a signal that comprises CSI from a terminal device, wherein the CSI comprises a rank indicator RI, indication information, and a second precoding matrix indicator PMI2; obtaining, by the network device, the RI and the indication information based on the signal comprising the CSI; obtaining, by the network device, the PMI2 based on the RI and the indication information; and determining, by the network device, a precoding matrix W based on the rank indicator RI and the second precoding matrix indicator PMI2, wherein W meets a formula W = W 1 × W 2, W is a matrix with Nt rows and L columns, W 1 is a matrix with Nt rows and 2I columns, W 2 is a matrix with 2I rows and L columns, Nt is a quantity of antenna ports, L is a rank indicated by the RI, Nt is greater than or equal to L, and I is an integer greater than or equal to 1; an element at a location in an i th row and an l th column in W 2 is Y i,l, i is an integer greater than or equal to 0 and less than or equal to 2I-1, l is an integer greater than or equal to 0 and less than or equal to L-1, Y i,l meets a formula Y i, l = X i, l 1 × X i, l 2 × X i, l 3, and X i, l 3 is a complex number with modulus 1; and the indication information is used to indicate that W 2 comprises M X i, l 1 whose values are not 0, the PMI2 is used to indicate a parameter of W 2, and the parameter of W 2 indicated by the PMI2 comprises all X i, l 1 in W 2 and X i, l 2 and X i, l 3, which are corresponding to X i, l 1 whose values are not 0, in W 2, and does not comprise X i, l 2 and X i, l 3, which are corresponding to X i, l 1 other than the M X i, l 1 whose values are not 0, in W 2. receiving, by a network device, a signal that comprises CSI from a terminal device, wherein the CSI comprises a rank indicator RI, indication information, and a second precoding matrix indicator PMI2; obtaining, by the network device, the RI and the indication information based on the signal comprising the CSI; obtaining, by the network device, the PMI2 based on the RI and the indication information; and determining, by the network device, a precoding matrix W based on the rank indicator RI and the second precoding matrix indicator PMI2, wherein W meets a formula W = W 1 × W 2, W is a matrix with Nt rows and L columns, W 1 is a matrix with Nt rows and 2I columns, W 2 is a matrix with 2I rows and L columns, Nt is a quantity of antenna ports, L is a rank indicated by the RI, Nt is greater than or equal to L, and I is an integer greater than or equal to 1; an element at a location in an i th row and an l th column in W 2 is Y i,l, i is an integer greater than or equal to 0 and less than or equal to 2I-1, l is an integer greater than or equal to 0 and less than or equal to L-1, Y i,l meets a formula Y i, l = X i, l 1 × X i, l 2 × X i, l 3, and X i, l 3 is a complex number with modulus 1; and the indication information is used to indicate that W 2 comprises M X i, l 1 whose values are not 0, the PMI2 is used to indicate a parameter of W 2, and the parameter of W 2 indicated by the PMI2 comprises all X i, l 1 in W 2 and X i, l 2 and X i, l 3, which are corresponding to X i, l 1 whose values are not 0, in W 2, and does not comprise X i, l 2 and X i, l 3, which are corresponding to X i, l 1 other than the M X i, l 1 whose values are not 0, in W 2.