Objective To explore the influence of different model scopes on acetabular stress distribution and optimal osteotomy result in preoperative planning of Bernese acetabular osteotomy. Methods Two patients with hip dysplasia were established according to different model ranges. Model 1 included the affected hip and femur, and Model 2 included the complete pelvis and affected femur. Compare and analyze the acetabular cartilage contact pressure, area and distribution of the two models under single-leg standing conditions, and simulate osteotomy. Results Compared with Model 1 before surgery, Model 2 had higher contact pressure, smaller contact area and closer distribution to the meniscus edge of acetabulum. Compared with 11 postoperative plans, the variation amplitude of contact pressure and the optimal osteotomy angle for Model 1 were all smaller than those of Model 2. Conclusions The preoperative analysis result of the model with affected hip bone and femur would underestimate the degree of stress concentration and misjudge the location of stress concentration, and the obtained optimal osteotomy rotation angle would be relatively small. The research findings provide certain theoretical basis for preoperative planning and modeling of osteotomy.