The paper focused on the effects of body dimensions of patients with spinal cord injury (SCI) on the spring locations of unpowered energy-stored exoskeleton (ES-EXO) based on energy-stored element optimization method. The optimal spring locations and muscle activations of patients with different combinations of height and weight were simulated in AnyBody Modeling System. The spring locations of ES-EXO changed slightly with height, and the weight affected the spring locations of S12 and S22 significantly. SCI patients with increasing height propelled themselves forwards by altering the muscle force distribution of latissimus dorsi, pectoralis major and deltoid, generating more obliquus internus abdominis (OI) and rectus abdominis force in support phase and less OI force in swing phase. SCI patients with increasing weight also adopted different distribution of thorax and shoulder muscle forces for ambulation. The patients with larger weight were likely to enhance OI force so as to provide sufficient hip flexion moment in swing phase.