Objective To investigate the imaging features of alar ligament and its extent, and provide the basis forclinical treatment.Methods 3.0 T superconducting MRI was used to scan the alar ligament with high resolution PDWI sequence (Proton density weighted imaging, PDWI)in 109 patients of emergency admissions due to head and neck trauma. Based on imaging features, ligamentous injury was classified into three degrees(Ⅰ to Ⅲ degrees).Patients with Ⅰ degree ligamentous injury were treated conservatively, andⅡtoⅢdegree injury patients were treated with surgery, then follow-up was performed with MRI for the recovery of ligaments and clinical evaluation for symptoms (6 months follow-up period). Results High-resolution PDWI showed 78 patients with no ligament injury.On follow-up, patients recovered well (atlantoaxial joint motor function and clinical symptoms). Thirty one patients had alar ligament injury in varying degrees, of which 18 patients had grade Ⅰ injury, nine patients had degree Ⅱinjury, and four patients had degreeⅢinjury .All gradeⅠinjury patients received conservative treatment. Follow-up of patients showed good recovery, MR revealed the lesions shrank in varying degrees or disappear. Six gradeⅡinjury patients had surgical treatment, and three received conservative treatment. On follow-up, seven patients had a good recovery, two patients underwent surgical treatment within 3 months after injury and recovered well.Three gradeⅢpatients treated by surgery, and all with good recovery postoperative, and a patient died of respiratory failure. Conclusions High resolution PDWI is an effective tool to evaluate the extent of the alar ligament injury. Grade Ⅰ ligamentous injury patients treated conservatively can achieve good results, GradeⅡandⅢligamentous injury patients should receive surgical treatment early.