Objective To study the magnetic resonance imaging findings of frozen shoulder so as to improve the diagnostic level of it. Methods A retrospective analysis of MR images was performed in 81 cases (81 patients) with clinically confirmed frozen shoulder in our hospital. The joint capsule edema sign (including anterior-superior, anterior-inferior, posterior-inferior, posterior-superior and wide range of edema), joint capsule thickening sign, rotator cuff interval edema sign, hydrops of capsule under coracoid process sign, coracohumeral ligament thickening/edema sign were observed and recorded and the features were summed up. Results The detection rate of joint capsule edema sign was 96.3%, with 33.3%, 87.7%, 59.3%, 56.8% and 80.2% of anterior-superior, anteriorinferior, posterior-inferior, posterior-superior and wide range of edema. The detection rate of joint capsule thickening sign was 59.3%. The detection rate of rotator cuff interval edema sign was 69.1%. The detection rate of hydrops of capsule under coracoid process sign was 40.7% and the detection rare of coracohumeral ligament thickening/edema sign was 24.7%. Conclusion Joint capsule edema sign, rotator cuff interval edema sign and joint capsule thickening sign had a higer detection rate in frozen shoulder and anterior-inferior edema edema was especially common within joint capsule edema sign. Coracohumeral ligament thickening/edema sign had a low detection rate in frozen shoulder.