A channel information reporting method and apparatus and a system are used to improve adaptive performance of a link. A first device includes: a receiving module, configured to receive a reference signal from a second device; a processing module, configured to: perform channel estimation based on the reference signal to obtain a channel matrix, decompose the channel matrix to obtain an unquantized precoding matrix, and generate channel information used to describe the unquantized precoding matrix; and a sending module, configured to send the channel information used to describe the unquantized precoding matrix to the second device. The second device sends the channel information used to describe the unquantized precoding matrix. Therefore, a quantization error is avoided, so that a precoding matrix obtained by the first device is more accurate, thereby effectively improving the adaptive performance of the link.