Abstract: The problem of Multi-tag collision is inevitable in the RFID system so that anti-collision algorithm is the key to realize the tag identification rapidly.In this paper,an improved binary search anti-collision algorithm is proposed based on some related anti-collision algorithm.This algorithm uses collision bits to construct quad tree,which reduces the search times and the amount of transmission information of readers to improve the system efficiency.The experimental results show that the proposed algorithm performs significantly better than the existing anti-collision algorithms.