Multi-tags collision has been considered as a critical problem in RFID system.Recently

many query tree protocols based on bit tracking technology have been presented for resolving the tag collision efficiently.However

their performance need to be further improved because of unused collided bits and idle slots.In this paper

a bit query based method is presented

which requires the tag to respond a mapped bit string instead of its ID sequence.Compared with traditional ID query

it not only eliminate idle queries

but also can separate collided tags into many smaller subsets and make full use of the collided bits as well.Based on this method

a novel query tree protocol bit query based M-ary tree(BQBMT)is proposed

which recursively resolves collisions by forming a M-ary tree

and optimally switches from bit query mode to ID query mode for quickly identifying the tags when tag is readable.Theoretical analysis and simulation results show that the system efficiency of BQBMT is close to 0.89

which outperforms the other existing QT-based and hybrid algorithms.