Disclosed are a communications method and device. The method includes: sending, by a network device, configuration information to a terminal device; determining, by the terminal device, channel state information CSI measurement behavior and/or CSI feedback related information, where the channel state information CSI measurement behavior and/or the CSI feedback related information are/is related to the configuration information; and performing, by the terminal device, CSI measurement based on the configuration information and the CSI measurement behavior and/or the CSI feedback related information, to obtain at least one piece of CSI, and sending all or some of the at least one piece of CSI to the network device. It can be learned that, in a scenario in which a plurality of transmission modes are supported, according to the foregoing method, the terminal device can measure CSI, and feed back the measured CSI to the network device.