Objective To evaluate the effects of hemipelvic reconstruction with the modular hemipelvic prostheses after acetabular resection. Methods From June 2003 to June 2004, limb-sparing reconstruction was performed in 8 patients with malignant periacetabular tumors. There were 6 male and 2 female patients. The median age was 45 years (range, 18～65 years). The primary malignant tumor was in 5 patients, including chondrosarcoma (3), osteosarcoma (1), and Ewing sarcoma (1). The metastatic disease was in 3 patients, including renal cell carcinoma (1), breast carcinoma (1), stomach carcinoma (1).The en bloc resection and reconstruction with the modular hemipelvic prostheses were performed in all patients with periacetabular malignant tumor. The oncologic and reconstructive complications were followed up. The postoperative function was analyzed according to Enneking method. Results The average follow-up was 13.6 months (range, 7～18 months) in the patients with primary malignant bone tumor. Of 3 patients with metastasis disease, 2 patients were alive at the most recent followup and 1 patient died at 9 months postoperatively. The median survival time was 12 months (range, 9～15 months).All patients showed improvements in hip pain control, ambulation after surgery. There was no local recurrence and distant metastases. After resection and reconstruction with the modular hemipelvic prosthesis, there was no prosthetic dislocation and leg length discrepancy. The postoperative complications were wound margin necrosis (2), suspected deep infection (1) and internal fixation loosening (2). The functional outcomes were excellent 3, good 3, pair 2 at three months postoperatively. Conclusions The modular hemipelvic prosthesis might satisfy the requirements of pelvic reconstruction and functional recovery after acetabular resection during a short-term followup, and the long-term results will be further investigated.