Embodiments of the present invention disclose a handover method, User Equipment (UE), and a network side device, which can shorten a handover delay of a control plane and an interrupt delay of user plane data. A handover method includes: obtaining, by a UE, a Time Advance (TA) of a target cell before a handover; and obtaining an Uplink Grant (UL Grant) sent by the target cell; and then sending a Handover Complete message to the target cell with the TA on a resource that is corresponding to the UL Grant.