RFID plays the core role in the internet of thing, tag-collision is a key issue and must be addressed for radio frequency identification. Aim at the problem of tag-collision in RFID system, this paper analyzed ALOHA algorithm and it's enhanced algorithm in detail. An new ALOHA algorithm based on Fibonacci Number was proposed, and the strategy of changing the frame length was established. The simulation indicated that the proposed algorithm can improve the throughput and load of RFID system.