A method, an eNodeB, and a system for timing adjustment to a component carrier are provided. The method includes the following steps: receiving an instruction signaling, in which the instruction signaling is used for instructing a downlink component carrier used as a timing reference for an uplink component carrier; and adjusting the uplink component carrier by using the downlink component carrier as timing reference time. Through the embodiments of the present disclosure, the downlink component carrier used as the timing adjustment reference for the uplink component carrier is specified in the sent instruction signaling. The timing reference time used by the terminal during the TA adjustment of the uplink component carrier may be clarified and the TA adjustment of the uplink component carrier may be accurately confirmed.