The RFID(Radio Frequency IDentification) is a technology that automatically identifies objects containing the electronic tags by using radio frequency. In RFID system, the reader needs the anti collision algorithm for fast identifying all of the tags in the interrogation zone. This paper proposes the tree based Anti Collision algorithm using Parity Bit(ACPB) to arbitrate the tag collision. The proposed algorithm identifies tags without checking all the bits in the tags. The reader uses the parity bit which is added to the tag IDs. If there are two collided bits in tags, then reader identify tags by the parity concept. The reader can identify two tags using ACPB algorithm. ACPB can reduce the number of the requests from the reader, thus it shortens the time of identifying all of the tags in the interrogation zone.