This application provides a data sending method and apparatus, and a terminal device. The method includes: determining, by a terminal device, a transmit power based on first information, where the first information includes at least one of the following information: information about a channel coding type of uplink control information in an uplink control channel, information about a length of a check code bit in the uplink control information, information about a quantity of resources occupied by an uplink reference signal in the uplink control channel, information about whether the uplink control channel is sent in a frequency hopping manner, or a transmission format of the uplink control channel; and sending, by the terminal device, the uplink control channel based on the transmit power, so that communication reliability and accuracy can be improved.