Embodiments relate to a control information transmission method, user equipment, and a base station. The control information transmission method includes: determining, by user equipment, a downlink control information (DCI) format of a downlink control channel corresponding to a first serving cell, where the first serving cell is a serving cell corresponding to the user equipment, and the DCI format is determined using a duplex mode of the first serving cell and a feedback manner of a hybrid automatic repeat request-acknowledgment (HARQ-ACK) corresponding to the first serving cell; and detecting, by the user equipment, the downlink control channel according to the determined DCI format.