For radio frequency identification systems, multiple tags exchange data with the reader and cause collision problems. It makes use of an improved multi-state binary search algorithm, which according to the features of tags collisions, make full use of the collision information which have been obtained, adopt sleep counting strategy, introduce preconditioning mechanism to effectively reduce the total number of commands sent and each parameter's length. Simulation results show that the algorithm can rapidly and effectively identify the electronic tags, and with the increasing tag number and tag code length, the advantages become more prominent.