Objective To observe the application effect of 3D printing model and simulated surgery in total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH).Methods A total of 60 patients with DDH admitted to Department of Orthopedics I of NO.922 hospital of Joint Logistic Support Force from August 2020 to December 2022 were selected as the research object，and 30 patients were divided into groups by random number table method.In group A，the THA was completed according to routine operation.In group B，3D printing technology was used to make a solid model of the affected hip for surgical scheme design and simulated surgery.In group A，there were 13 males and 17 females.The patients’ age ranged from 36 to 69 years，with a mean of (54.81±7.03) years.In group B，there were 10 males and 20 females.The patients age ranged from 35 to 70 years，with a mean of (52.09±7.44) years.The operation indexes，postoperative recovery indexes，matching rate of prosthesis before and after operation，incidence rate of intraoperative femoral condyle fracture，postoperative acetabularfemoral anteversion angle，incidence rate of complications and hip joint function (Harris hip score，HHS) before and 4 weeks after operation were compared between the two groups.Results The intraoperative blood loss in group B was less than that in group A，the operation time，postoperative ground time，and hospital stay in group B were shorter than those in group A (P＜0.05).The matching rate of prosthesis before and after operation in group B (90%) was higher than that in group A (30%)，and the incidence rate of intraoperative femoral condyle fracture (0%) was lower than that in group A (50%) (P＜0.05).At 4 weeks after operation，HHS score in both groups were higher than those before operation (P＜0.05)，bue there was no significant difference between the two groups (P＞0.05).There was no significant difference in postoperative acetabular-femoral anteversion angle between the two groups (P＞0.05).No complications such as femoral and sciatic nerve injury，prosthesis loosening and dislocation，pulmonary embolism，lower limb deep vein thrombosis，periprosthetic fracture，and joint infection occurred in both groups.Conclusion The application of 3D printing model and simulated surgery in THA for DDH patients has a definite effect，which can improve the matching rate of prosthesis，reduce the incidence rate of intraoperative femoral condyle fracture，shorten the operation time，reduce the intraoperative blood loss，and promote rehabilitation，which is worth to be promoted and applied in the clinic.