Abstract: [Abstract] Objective：To observe the resorption and healing process of replanted tooth in experimental rats, so we can assist the doctor to cure and prevent the root resorption in clinic. Methods: The experiment was carried out on thirty 6-week-old SPF Wistar male rats(n=5) ,the rats were randomly separated into six groups,and one of which is blank group. The bilateral maxillary first molars of each rat in experimental groups were extracted, randomly chose one molar to replant in the socket immediately, and the other one experienced delayed replantation. The rats were sacrificed on day 1, day 3, day 7, day 14 and day 21 after replantation. Then we segregated the maxillaes and scanned the specimens with X-ray. After decalcification, tissue slices were made and stained with HE. Results: The shadow area around the replanted tooth expanded over time, especially in the delayed replant group; the histological reaction of the tooth displayed that the resorption lacune around the root grew more and bigger with the developing inflammation, then the pulp tissue and periodontal ligament began to recover themselves in immediate replant group and aveolar bone recovered strongly with root and periodontal ligament insteaded by bone like tissue in delayed replant group. Conclusions: The reaction of replanted tooth showed mainly inflammation at first and recovery at last. The prognosis of replanted tooth mainly depend on the vitality of periodontal ligament cells.