This application provides a communication method and a related device. In the method, a first reference signal sent by a first communication apparatus is for determining first channel information corresponding to K ports in N ports of the first communication apparatus, and the first channel information is for determining second channel information corresponding to the N ports. In other words, after a receiver of the first reference signal can determine, based on reference signals corresponding to the K ports, the first channel information corresponding to the K ports, the receiver can further determine the channel information corresponding to the N ports, where K is less than N.