Objective To explore the effect of MSCT 3D scanning and reconstruction on developmental dysplasia of the hip（DDH）in adult patients with total hip arthroplasty， The predictive value of acetabular prosthesis selection and osteotomy accuracy in THA. Methods Selection in our hospital between February 2021 and February 2023 were 60 adult DDH patients underwent total hip replacement， which USES routine preoperative planning as a control group of 30 patients，and using MSCT + reconstruction of 3 d scanning technology as observation group of 30 patients，planning after the completion of the planning of the surgical operation and implant placement， Relevant information was collected before and after the operation of the two groups. Operation time，intraoperative blood loss，intraoperative fluoroscopy time， acetabular prosthesis selection and matching rate， femur split fracture rate， pelvis and acetabular reduction quality， Majeed score and Harris hip function score were compared between the two groups. The osteotomy distance and sharp shoulder distance of the two groups were compared before planning and in actual conditions，and the correlation between MSCT 3D scanning and reconstruction technology and the accuracy of acetabular prosthesis selection was evaluated. Results Results analysis showed that MSCT 3D scanning+reconstruction technology used in preoperative evaluation of patients in the observation group was correlated with the accuracy of acetabular prosthesis selection（P < 0.05）， and the absolute errors of osteotomy distance and sharp shoulder distance of patients in the observation group were smaller than the actual situation before planning（P < 0.05）. In addition，compared with the control group， the operative time，intraoperative blood loss， intraoperative fluoroscopy time and incidence of femoral split fracture in the observation group were significantly lower，and the matching rate of acetabular prosthesis selection，the Majeed scores and Harris scores were significantly higher in the following 3 months were significantly higher（P < 0.05）. The reduction quality of pelvis and acetabulum was not statistically significant between the two groups（P > 0.05）. Conclusion Msct?based 3D scanning + reconstruction has a high predictive value for the selection of acetabular prosthesis and the accuracy of osteotomy in adult DDH total hip replacement， and the use of this technology for preoperative planning has a significant optimization effect on the actual treatment effect and patient recovery.