[Objective] To evaluate the safety and short-term efficacy of 3D printed customized semi-pelvic prosthesis for pelvis reconstruction after pelvic tumor resection. [Methods] The medical records of 12 patients with pelvic tumor admitted to the Second Department of Orthopedic Surgery of Yunnan Cancer Hospital from January 2022 to April 2023 were retrospectively analyzed, including 7 males and 5 females, with an average age of 38.5±21.61 years. 5 cases were metastatic tumors and 7 were primary tumors. 5 tumors invaded areas I and II, 4 invaded areas II and III, 1 invaded areas I, II and III, 1 invaded areas I and IV, and 1 invaded areas III and IV. [Results] All the 12 patients were followed up for 7.17±4.02 months. The preoperative score of MSTS was 11.00±4.77 and the postoperative score was 16.25±2.93. Harris' preoperative score was 46.67±5.38 and postoperative score was 64.83±7.28. [Conclusion] It is a safe and effective method for pelvic tumor reconstruction to reduce pain and recover function in patients with short-term follow-up after reconstruction of pelvic tumor resection by 3D printing customized semi-pelvic prosthesis.