The functional reconstruction of complex pelvic defects has remained a globally recognized challenge. To address this challenge, a personalized 3D-printed tantalum-coated titanium alloy pelvic reconstruction prosthesis was independently developed, aiming to enhance the osteogenic activity of existing titanium alloy prostheses. This study was designed to determine the efficacy, safety, and early clinical outcomes of this novel prosthesis. A prospective randomized controlled trial enrolled 21 patients with complex pelvic defects who met the inclusion and exclusion criteria. The patients were randomly divided into an experimental group (11 cases of personalized 3D-printed tantalum-coated titanium alloy pelvic reconstruction prostheses) and a control group (10 cases of uncoated prostheses). Personalized 3D-printed titanium alloy pelvic reconstruction prostheses were designed and fabricated using preoperative patient imaging data. Prostheses in the experimental group underwent plasma immersion ion implantation (PIII) to deposit an approximately 15μm tantalum coating. After post-treatment and sterilization, the prepared prosthesis was installed accurately according to the plan during the operation. After operation, the prosthesis was examined by imaging, and the surgical time, intraoperative blood loss and abnormal laboratory indexes were compared between the two groups. Regular postoperative follow-up assessments were conducted, with all postoperative complications systematically documented during the follow-up period. Postoperative imaging evaluation was performed to comparatively analyze bone ingrowth at the prosthesis-bone interface between the two groups. Harris Hip Score was used to evaluate the lower limb function of the two groups at the last follow-up. All 21 procedures were successfully completed with primary wound healing and no early complications. All patients were followed up, with an average follow-up time of 15.1±7.1 months. There was no statistically significant difference in the comparison of operation time, intraoperative blood loss, and abnormal laboratory indexes between the two groups of patients (P>0.05). The shape of the pelvic reconstruction prosthesis was highly matched with the bone defect in all patients, and the stability was good. One patient in the experimental group experienced periprosthetic infection and one patient experienced dislocation of the artificial femoral head; Two cases of periprosthetic infection and one case of artificial femoral head dislocation occurred in the control group of patients. At final follow-up, the Harris Hip Score was significantly higher in the experimental group compared to the control group, and the difference was statistically significant (P<0.01); The excellent/good rate of bone ingrowth at the prosthesis-bone interface was significantly higher in the experimental group (90.9%) than in the control group (30.0%, P<0.001).The independently developed personalized 3D-printed tantalum-coated titanium alloy pelvic reconstruction prosthesis, fabricated using PIII technology, which can promote bone ingrowth, enhance the stability of the prosthesis, improve lower limb function of patients, represents an effective approach for reconstructing complex pelvic defects.