A method for feeding back information about a channel between antenna arrays is provided, which includes: receiving, by a first network device, channel information of N×M sub-channels that is sent by a second network device, where an antenna array of the first network device includes M subarrays, an antenna array of the second network device includes N subarrays, a channel between the antenna array of the first network device and the antenna array of the second network device includes the N×M sub-channels, M and N are positive integers and are not both 1, and the M subarrays and the N subarrays each include at least two antennas; and generating channel information of the channel between the antenna array of the first network device and the antenna array of the second network device according to the channel information of the N×M sub-channels that is from the second network device.