Tag collision avoidance is critical to the success of data communications in radio frequency identification (RID) system. Many classic algorithms are similar to QT, CTT, etc., and cannot meet the needs of higher and higher parameters. So based on QT and CTT, we propose an improve group anticollision algorithm(IGQT) to improve the performance of RFID system. First, we compare the algorithmic processes in QT and CTT, and compare and analyze the pros and cons of the two algorithms. Then, we reduce the number of slots and reduces the number of queries based on the QT and CTT algorithm, final, compare the system throughput and number of slots of QT, CTT, and IGQT algorithms. Experiment shows, the IGQT algorithm outperforms the existing proposed algorithms and greatly improves the recognition rate of the entire system.