Subacromial impingement syndrome (SIS) is defined as pressurization and impingement between the acromion, the bursa under the acromion, and the rotator cuff during the abduction and elevation of the shoulder joint, resulting in pain and a functional disturbance of elevation. It is the most common disorder of the shoulder, accounting for 44-65% of all complaints of shoulder pain during a physician's office visit. The study was performed with the aim of valuing the magnetic resonance imaging (MRI) and computed tomography (CT) in diagnosing patients with SIS. A total of 68 patients with SIS were selected as study subjects and subjected to MRI and CT examinations. The diagnostic accuracy and sensitivity of MRI and CT were, respectively, 97.06 and 70.59% (P<0.05); the detection rates of SIS grade I, grade II, and grade III by MRI were 91.67%, 96.77%, and 100%, respectively, which were significantly higher than 50%, 80.65%, and 68% by CT, respectively (P<0.05). MRI and CT detection indicated that there was no significant difference in extensive rotator cuff tear, acromion stenosis, and normal acromion detected by MRI and CT (P>0.05). In conclusion, the diagnostic accuracy, sensitivity, and detection rate of acromion of MRI were higher compared with those of CT examination, and MRI is more suitable in the clinical diagnosis of SIS.