The present invention discloses a method, a device, and a system for transmitting uplink control information, and relates to the communications field. The method includes: encoding uplink control information to acquire a coded bit sequence of the uplink control information, where the uplink control information includes first uplink control information and second uplink control information; and transmitting the coded bit sequence of the uplink control information to a base station through a physical uplink channel. The system includes a user equipment and a base station. By encoding uplink control information to acquire a coded bit sequence of the uplink control information and transmitting, through a physical uplink channel, the coded bit sequence to a base station, the present invention supports simultaneous transmission of first uplink control information and second uplink control information and improves transmission performance.