Abstract: [Abstract] Objective ：To observe the clinical effects of Physiologic Anchorage Control technique in the treatment of maxillary lip-opposite low canine and severely crowding . Methods: 20 patients with maxillary lip-opposite low canine and severely crowed teeth were included, their average years were 14.5. They were extracted 4 first premolars and treated with PASS appliance .Analysis was carried out before and after treatment．Results: After treatment，normal overbite ,overjet and good occlusal relationship were achieved. The upper first molar showed mesial displacement of 1.56±1.1mm, no significant change was found after treatment． Conclusions ：Physiclogic Anchorage Control technique could be effectively and conveniently used in the treatment of patients with severely crowed malocclusion

Key words: [Key words] Physiclogic Anchorage Control technique, PASS appliance, anchorage