This application discloses a message sending method, a message receiving method, an apparatus, and a device. The message sending method includes: A network device sends, by using a physical downlink control channel (PDCCH), downlink control information (DCI) with s a cyclic redundancy check (CRC) bit, wherein the DCI is in a first DCI format or a second DCI format, wherein the DCI is used to indicate to a terminal device to enter a sleep mode at a first moment. The network device receives a response message sent by the terminal device in response to the DCI.