Objective To observe the MRI imaging manifestations of the ligaments and soft tissues around the atlanto-axial joint in children with atlanto-axial rotation instability.Methods Assigned into observation group were 50 children with atlantoaxial rotatory displacement who had been treated in our hospital from January 2013 to March 2014.Another 50 healthy children were chosen as a control group who underwent health check-ups during the same period in our hospital.Both groups received MRI examinations of the ligaments and soft tissues around the atlantoaxial joint using the same equipment and methods.MRI manifestations and characteristics of the ligaments and soft tissues around the atlantoaxial joint were analyzed and compared between the 2 groups.Results In the observation group,odontoid gap asymmetry appeared on both sides,with left shift in 32 cases and right shift in 18 cases.The MRI imaging PDWI sequence showed a significant better diagnostic sensitivity than the other sequences (T1WI,T2WI and SPAIR) (P ＜ 0.05).The MRI examinations on all the children with different sequences found 50 cases of degree Ⅰ lesion in the observation group and 4 cases of degree Ⅰ lesion in the control group,and 12 cases of degree Ⅱ lesion in the observation group and none degree Ⅱ lesion in the control group,showing a significant difference between the 2 groups regarding the diagnostic sensitivity of lesions of degrees Ⅰ and Ⅱ (P ＜ 0.05).Conclusions MRI can clearly show the rotation displacement of atlanto-axial joint associated with transverse ligament,alar ligament and lesions of the surrounding soft tissues.MRI has a dcfinite diagnostic value for atlanto-axial rotation displacements in children,especially those caused by transverse ligament tear after trauma.