The ability of simultaneously identifying many tags is crucial for many RFID applications. EPC Gen-2 protocol specified Slotted Random (SR) algorithm to solve tag collision problem. In this paper, an Active Slotted Random (ASR) algorithm which is an improved SR algorithm was proposed. Two slot random-redistribute commands are introduced to make the collision tags redistribute in the adjacent and increase the response slot of other tags, which will lead to relative average slot distribution of tags. Simulation results shows that the proposed ASR algorithm observably improve the tag throughout by 30 percent compared with SR algorithm. It is without question that ASR will contribute to improve the performance of EPC Gen-2 RFID system because the reader can identify more tags with shorter time.