Objective To study the effects on anterosuperior stability of the shoulder joint when the coracoacromial arch is damaged at different degrees. Methods Thirty-six specimens of the fresh frozen adult shoulder joints were randomly and evenly divided into 3 groups. Group 1, reserving integrity of the coracoacromial ligament of the shoulder joint; Group 2, dissecting half of the coracoacromial ligament attachment sector on the acromion; Group 3, grinding all the coracoacromial ligament attachment sector on the acromion. The specimens of the shoulder joint were fixed on test bench of the biomechanical testing machine. The axial pressure was applied on the humeral shaft, and the humeral head was pushed to move in anterosuperior direction. The displacement distance of the humeral head under 50 N pressure was then recorded. Results Under 50 N pressure, the displacement distance of the humeral head in Group 1, 2, 3 was (2.50±0.59), (5.38±0.71), (6.49±0.81) mm, respectively, which showed significantly statistic differences among 3 groups (P<0.05). Conclusions The damage to the coracoacromial arch will affect the anterosuperior stability of the shoulder joint. The greater damage to the coracoacromial arch will lead to the lower anterosuperior stability of the shoulder joint.