Abstract: Radio frequency identification (RFID) is a critical technology which can realize the unique identification of objects through radio frequency signals. However, with the wide application of RFID technology, the number of tags is gradually increasing, and the demand for RFID system performance is also growing. Among the many demands, the anti-collision capability of the system is a widely considered application requirement. In this paper, we first briefly introduce the RFID system process and the traditional anti-collision strategy. Then, it focuses on the improved physical layer-based collision avoidance strategy. The improved anti-collision strategy is analyzed from four aspects: reader strategy, antenna size, channel and link, and tag size. Finally, the technical challenges in the current system are summarized, and the future direction of the RFID system is overlooked.