Objective To explore the learning curve of Bikini incision direct anterior approach total hip arthroplasty(Bikini-THA).Methods Clinical data of 80 cases of Bikini-THA initially completed by an operator skilled in posterolateral approach and direct anterior approach total hip arthroplasty from March 2020 to March 2023 were retrospectively analyzed,and the learning curve was observed by scatter plots of operative time and intraoperative bleeding.They were divided into groups A to D according to the order of surgery,with 20 cases in each group.The operative time,intraoperative bleeding,acetabular abduction angle,anteversion angle,angle between stem and femoral axis,postoperative hip Harris score and complications were compared among the 4 groups.Results After about 40 cases,the decreasing trend of operative time and intraoperative bleeding slowed down and stabilized.The operative time and intraoperative bleeding in the 4 groups were group A＞group B＞groups C and D(P＜0.05),and the differences between the group C and group D were not statistically significant(P＞0.05).The acetabular prosthesis was well-positioned in the 4 groups(abduction angle of 30°-50°,anteversion angle of 5°-25°).The femoral prosthesis center fixation rate(angle between stem and femoral axis ≤3°)was group A＜groups C and D(P=0.003,0.003).The differences in the Harris scores of the hip joints at 2 weeks,1 month,3 months,and 12 months postoperatively of the 4 groups were not statistically significant(P＞0.05),and the efficacy evaluations of the hip joints at 12 months postoperatively were all excellent.There were 5 cases of complications in the group A(2 cases of greater trochanter fracture and 3 cases of lateral femoral cutaneous nerve injury),3 cases of complications in the group B(1 case of greater trochanteric fracture,1 case of lateral femoral cutaneous nerve injury,and 1 case of incision infection),1 case of complications in the group C(lateral femoral cutaneous nerve injury),and no complications in the group D.The follow-up period lasted for 12-26 months,with a mean of(19.4±4.7)months.There were no complications such as dislocation or loosening of the prosthesis.Conclusion The Bikini-THA learning curve was approximately 40 cases.