The present invention discloses a cell handoff method and a UE based on a TDD system. A UE measures received pilot channels of a source cell and a neighboring cell according to a measurement control message and reports measurement result to a RNC. The RNC, determines whether a target cell to be subject to a cell handoff process has available resources at a time slot different from that of the source cell and if yes, transmits a cell handoff command to the UE, allocates available resources for the UE in the target cell and transmits traffic carrier data of the UE to the source cell and the target cell respectively. After receiving the cell handoff command, the UE communicates with the source cell and the target cell at a same frame and at same time according to the allocated available resources.