Abstract: Focusing on the problem of the binary search anti-collision algorithm in RFID system such as many search times and large amount of communication data, a new anti-collision algorithm for RFID with counter and bi-slots was proposed based on regressive search tree algorithm and time slot algorithm. The tags are searched step by step according to the slot counter in tag and the collision bit information that received by reader. The response tags are divided into two groups, respectively return data information to the reader in two time slot. The reader sends only the information of the highest collision bit position; Tags return only the bits of data after the highest collision bit. Theoretical analysis and simulation results show that the new algorithm is superior to other common anti-collision algorithms, which greatly reduces the search times and communication data, and improves the efficiency of the search.