Embodiments of the present invention provide a UMTS-to-LTE network handover method, device and system. In a co-site scene, a handover command transmitted from a source RNC to UE includes an indication that an RACH process in a target cell is not needed, an uplink resource of a handover complete message transmitted by the UE is pre-allocated in advance, the value of TA is determined by the source RNC in advance, the handover command carrying the indication, the uplink resource and the TA value are transmitted to the UE, and the UE can directly access to the target cell after receiving the handover command without performing the RACH process in the target cell, so that interrupt delay caused by the RACH process is shortened, and the related resources of the RACH are also saved.