The present disclosure relates to methods and apparatus for transmitting uplink control information. One example method includes generating, by a terminal device, an encoded uplink data packet, where the uplink data packet belongs to an uplink channel, the uplink channel is carried on a candidate time-frequency resource in a first time transmission interval (TTI), the candidate time-frequency resource is a first time-frequency resource or a second time-frequency resource, and a second time-domain start point of the second time-frequency resource is later than a first time-domain start point of the first time-frequency resource, performing, by the terminal device, detection on a carrier in which the candidate time-frequency resource is located, and sending, by the terminal device, the uplink channel on the candidate time-frequency resource based on a result of the detection, where the uplink channel includes uplink control information and the encoded uplink data packet.