Abstract: Objective To investigatethe clinical significance of hip rotation center location after reconstruction with modular hemipelvic prostheses for periacetabula tumors. Methods Forty-two patients who received periacetabular tumor resection and reconstruction with modular hemipelvic prosthesis between January 2004 and January 2014 in our institute were included. Postoperative complications, function (measured by MSTS score), survival rate and recurrence rate were analyzed. The position of prosthetic hip rotation center was measured. By its deviation angle from the ideal rotation center, the patients were divided into inward group, normal group and outward group in the horizontal level, and upward group, normal group and downward group in the vertical direction. And the relationship between positional difference of prosthetic hip rotation center and function at 1 month, 3 months, 6 months and 12 months after surgery was analyzed. Results Of forty-two cases in total, 25 patients were male and 17 patients were female. The age of the patients ranged from 12 and 69 years (median, 38 years).The minimal followup period was 12 months (mean,36 months; range,12-86 months).The complication rate was 31.0% and hip dislocation rate was 7.1%. The overall survival rate was 69.4% at 3 years and 43.7% at 5 years. After 1 month, 3 months, 6 months, the function of the reconstructed hip gradually improved, with MSTS score showing an increasing trend. The MSTS scores at these three time points were compared, the difference was statistically significant (P<0.05). The improvement of function after 6 months and 12 months was not obvious, with the difference not being statistically significant (P> 0.05). The deviation of hip rotation center in the longitudinal direction and the horizontal direction did not affect the function of the hip (P>0.05). Conclusion It is safe and effective for patients with pelvictumorto receive modular hemipelvic prosthesis reconstruction once the prosthesis is fixed in the most firmly position, where soft tissue fully covered, the muscles could be rebuilt more easily andwhere the eccentricity of the femoral got a certain degree of recovery. The relationship between the deviation of hip rotation center and postoperative function needs to be confirmed.