Abstract: Objective: To analysis the Changes of Temporomandibular Joint（TMJ) Under +Gz Condition. Methods: 60 male Wistar rats were randomly divided into 5 groups （n=12). Group A was normally fed. G roup B was only fixed with rat kept devices for 5 minutes Group C was borne + 1Gz for 5 minutes. Group D was repeatedly exposed +10Gz （each for 30s, onset rate about 0.5G/s, 3 times/d with +1Gz 1 minute intervals, 3d/wk, 3 weeks in total) In group E 5 times/d and 4d/wk, other variables is the same as group D Temporomandibular Joints and masticatory muscles from each group were respectively taken out and observed under microscope and SEM. Results: No abnormal changes were observed in group A B and C But in Group D and E pathologic injuries were seen in TMJ and masticatory muscles in different degrees In group D, it can be seen that the arrangernent disorder disruption of collagen fibers The gel like substances become very thin but roughly integrated In group E, because most gel like substances disappeared, the dispose and breakdown of collagen fibers of condyle of mandible and Joint disc were found Some fibroblast cells were taken from the condyle Conclusion: The TMJs were induced pathologic changes in different degrees under various experimental variables The increasing +Gz exposure could lead to the heavier damage of Rat’s TMJ