[Objective]To probe the efficacy of total hip arthroplasty(THA)in the treatment of patients with ankylosing spondilitis(AS).[Method]Ninety-eight THA were performed in 56 patients who had AS,and 42 patients(76 hips)were analyzed retrospectively with an average follow-up period of 5.6 years(ranged,2.5 to 5.5 years).The clinical results were evaluated by the Harris hip scoring system and radiographic analysis.[Result]For the latest follow-up,the average Harris hip score improved from 26.8 points(ranged,4 to 51 points)preoperatively to 85.2 points(ranged,55 to 94 points)at the final postoperatively evaluation.89.5% of the patients had an excellent or good results evaluated by Harris hip scoring system postoperatively.One patient was revised for infection,fissured fracture of neck of femur or calcar femorale above the lesser trochanter happended in two patients,one patient had footdrop and recovered 3 months later,1 patient had deep vein thrombosis.There was no sign of loosening,dislocation or fracture of the prosthesis.According to the system of Brooker,the incidence of heterotopic ossification was 9.2 %(7 hips).[Conclusion]THA can greatly relieve the pain of the patients who have AS and reconstruct the function of hip joint.Compared with THA operated for other cause of disease,THA in AS leads to no high risk.