In a control information sending method, a network device sends first physical layer control information to a first terminal device, where the first physical layer control information indicates a first index to the first terminal device, and instructs the first terminal device to monitor second physical layer control information within a first time period. The network device sends the second physical layer control information to at least one terminal device within the first time period, where the second physical layer control information includes at least one control information field, the at least one control information field includes a first control information field, and the first control information field instructs the first terminal device to receive or send data, or the first control information field instructs the first terminal device to receive or send data or not to receive or send data.