Objective To evaluate the mechanical behavior of elbow internal soft tissue at different healing stages of posterior capsular injury. Methods A finite element model of the elbow joint, including muscle activation behavior, was established to simulate the elbow flexion at no injury and 2, 4, 6, and 8 weeks after posterior capsule injury. The von Mises effective stress variation of articular capsule, ulnar cartilage and ligaments were analyzed. Results At no injury and 2, 4, 6 and 8 weeks, the stress of the articular capsule at 60° flexion were 8.23 MPa, 7.87 MPa, 8.27 MPa, 8.99 MPa and 10.5 MPa, respectively. When elbow flexion angle was 30°, ulnar cartilage stress increased by 13.0%, 28.3%, 41.3% and 43.5% at 2, 4, 6 and 8 weeks, respectively, compared with no injury. At 4 weeks, compared with 2 weeks, the stress of the radial collateral ligament at 15°, 30°, 45°, 60° and 75° was reduced by 12.5%, 22.2%, 13.6%, 3.2% and 10.6%, respectively. Conclusion The results provide theoretical basis for the prevention and treatment of capsular contracture and the development of rehabilitation AIDS.