Objective To compare the biomechanical effects between rotational acetabular osteotomy and Chiari osteotomy for developmental dysplasia of the hip (DDH) by biomechanical test. Methods Sixteen DDH models of 8 human cadaver specimens were prepared by resecting the upper edge and posterior edge of acetabulum. And the Wiberg central-edge angle (CE) of the DDH model was less than 20°. Then the rotational acetabular osteotomy was performed on the left hip and Chiari osteotomy on the right hip. When 600 N loading was loaded at 5 mm/minute by a material testing machine, the strain values of normal specimens, DDH specimens, and 2 models after osteotomies were measured. Results In normal specimens, the strain values of the left and right hips were 845.63 ± 533.91 and 955.94 ± 837.42 respectively, while the strain values were 1 439.03 ± 625.23 and 1 558.75 ± 1 009.46 respectively in DDH specimens, which was about 2 times that of normal hips. The morphology and X-ray examinations indicated that the DDH model was successfully established. The strain value was 574.94 ± 430.88 after rotational acetabular osteotomy, and was significantly lower than that of DDH specimens (t=4.176, P=0.004); the strain value was 1 614.81 ± 932.67 after Chiari osteotomy, showing no significant difference when compared with that of DDH specimens (t=0.208, P=0.841). The strain value relieved by rotational acetabular osteotomy was significantly higher than that by Chiari osteotomy (t= — 2.548, P=0.023). Conclusion Rotational acetabular osteotomy is better than Chiari osteotomy in relieving hip joint stress of DDH.