Embodiments of the present invention provide a channel state information transmission method, user equipment, and an access network device, to resolve at least a prior-art problem that multiple pieces of CSI cannot be simultaneously transmitted. The method includes: receiving, by UE, downlink data from an access network device; determining, by the UE, an uplink subframe used to send feedback information of the downlink data, where a first downlink subframe set associated with the uplink subframe includes a first subset and a second subset, and the first subset is a proper subset of the second subset; determining, by the UE, a channel resource used to send the feedback information, where the channel resource includes a first uplink channel resource or a second uplink channel resource; and if sending of r pieces of CSI is configured in the uplink subframe for the UE, a codebook size of the feedback information corresponds to the first subset, and the channel resource determined by the UE is the second uplink channel resource, sending, by the UE, the feedback information and t pieces of CSI of the r pieces of CSI on the second uplink channel resource.