Objective To establish preoperative and postoperative femoral-pelvic-lumbar spine models of patients with developmental dysplasia of the hip (DDH) and healthy volunteers and to study the biomechanical effects of curved periacetabular osteotomy on the lumbar spine. Methods: Preoperative and postoperative femoral-pelvic-lumbar spine DICOM and Communications in Medicine data from four patients with DDH and one healthy volunteer were acquired using CT scanning technology, and a three-dimensional finite element model was constructed. The offset method was used to divide the cortical and cancellous bones in Geomagic and the lumbar cartilage, sacroiliac joint, pubic symphysis, and other cartilages were added to SolidWorks. The model was analyzed using ANSYS for finite element analysis, and the gait was the mid-stage of single-leg support during slow walking. The biomechanical changes in the lumbar spine of patients with DDH before and after surgery were analyzed and compared, and the biomechanical data of the lumbar spine of patients after surgery were compared with those of healthy volunteers. Results The femoral-pelvic-lumbar spine models of four patients and a healthy volunteer were established. The results obtained by the established models under each working condition were within the range of the referenced literature, and the validity of the models was proved. The postoperative stresses on the lumbar spine, femoral neck, annulus fibrosus, and nucleus pulposus were much smaller than those of the patients in the preoperative state, and the postoperative stresses on the lumbar spine, femoral neck, annulus fibrosus, and nucleus pulposus of the patients were similar to those of healthy volunteers. Conclusions: Curved periacetabular osteotomy significantly reduced the stresses on the lumbar spine and intervertebral discs. Additionally, the stresses on the annulus fibrosus were more uniform after surgery, which indicated that curved periacetabular osteotomy will adjust patients to a healthy state. This study provides a biomechanical basis for the clinical treatment of DDH and helps optimize surgical plans.