The anti-collision algorithm is the key technology of radio frequency identification system to a- chieve multi-target recognition. To solve the problem of too many identification times and transmitted bits in some binary tree based sehemes,a new tree-based anti-collision algorithm is proposed. The algo- rithm divides tags into several groups. Four query prefixes which consist of two bits are directly used to split tag set, and the backtrack strategy is adopted to reduce identification times. The simulation results show that the algor...