A channel state information, CSI, transmission method, wherein the method comprises: receiving, by user equipment, UE, downlink data from an access network device; determining, by the UE, an uplink subframe used to send feedback information of the downlink data, wherein a first downlink subframe set associated with the uplink subframe comprises a first subset and a second subset, wherein the first downlink subframe set includes downlink subframes corresponding to multiple carriers configured for the UE, the second subset includes downlink subframes on at least two carriers of the multiple carriers, and the first subset is a proper subset of the second subset, and the feedback information is used to indicate whether the UE successfully receives the downlink data; determining, by the UE, a channel resource used to send the feedback information, wherein the channel resource comprises a first uplink channel resource or a second uplink channel resource, the first uplink channel resource is a resource that at most support feedback of feedback information with a codebook size p, and the second uplink channel resource is a resource that at most support feedback of feedback information with a codebook size q, wherein q > p, q ≥ q1, p ≥ p1, p1 is a codebook size that is of feedback information and that corresponds to the first subset, q1 is a codebook size that is of feedback information and that corresponds to the second subset, and a codebook size is a quantity of original bits of feedback information before coding, and p, q, p1, and q1 are all positive integers; 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, wherein r ≥ 2, 2 ≤ t ≤ r, and r and t are both positive integers. receiving, by user equipment, UE, downlink data from an access network device; determining, by the UE, an uplink subframe used to send feedback information of the downlink data, wherein a first downlink subframe set associated with the uplink subframe comprises a first subset and a second subset, wherein the first downlink subframe set includes downlink subframes corresponding to multiple carriers configured for the UE, the second subset includes downlink subframes on at least two carriers of the multiple carriers, and the first subset is a proper subset of the second subset, and the feedback information is used to indicate whether the UE successfully receives the downlink data; determining, by the UE, a channel resource used to send the feedback information, wherein the channel resource comprises a first uplink channel resource or a second uplink channel resource, the first uplink channel resource is a resource that at most support feedback of feedback information with a codebook size p, and the second uplink channel resource is a resource that at most support feedback of feedback information with a codebook size q, wherein q > p, q ≥ q1, p ≥ p1, p1 is a codebook size that is of feedback information and that corresponds to the first subset, q1 is a codebook size that is of feedback information and that corresponds to the second subset, and a codebook size is a quantity of original bits of feedback information before coding, and p, q, p1, and q1 are all positive integers; 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, wherein r ≥ 2, 2 ≤ t ≤ r, and r and t are both positive integers.