Objective To investigate the clinical application effect of 3D printing personalized acetabular prosthesis in the reconstruction of complex elderly hip fractures with acetabular bone defects. Methods A retrospective analysis was conducted on the clinical data of elderly patients with complex hip fractures and acetabular bone defects who were admitted to Lanxi People’s Hospital from January 2024 to January 2026. All patients were evaluated by dual energy X-ray absorptiometry (DXA) before the operation, and were divided into subgroups according to the Paprosky acetabular bone defect classification. All patients underwent acetabular reconstruction using 3D printing personalized titanium alloy prostheses, which were designed based on the pre-operative computed tomography (CT) scan data. The changes in the Harris hip score (HHS), visual analogue scale (VAS), and leg length discrepancy (LLD) were compared between the pre - operative period and the last follow - up. The bone integration rate and HHS score were compared between the Paprosky II type and III type defect groups. The imaging manifestations of the patients and the occurrence of postoperative complications were recorded. Results During the study period, a total of 112 patients were screened, and 80 patients were finally included. The average follow-up duration was (15.6±4.2) months. Compared with the preoperative state, the patient’s HHS score significantly increased, the VAS score significantly decreased, and the LLD significantly shortened (all P＜0.001) at the last follow-up. The subgroup analysis results showed that there were no statistically significant differences in bone integration rate and HHS score between the Paprosky type II and type III defect groups (all P＞0.05). The imaging analysis showed that all the prostheses were in good position and the initial stability was satisfactory. At the last follow-up, no patient showed any clear radiological loosening or fracture. The incidence of postoperative complications was 6.25% (5/80), and all complications were cured after symptomatic treatment. Conclusion The 3D printing personalized acetabular prosthesis can precisely match the acetabular bone defect, providing excellent initial stability for the prosthesis, promoting postoperative bone integration, significantly improving the joint function of patients and alleviating pain. The short-term therapeutic effect is satisfactory.