OBJECTIVE： To study therapeutic efficacy of total hip arthroplasty （THA） combined with Alendronate sodium tablets in the treatment of femoral neck fracture and its effects on bone mineral density （BMD）. METHODS： A total of 98 patients with femoral neck fractures in our hospital during 2014-2016 were divided into observation group and control group by random digital table method， with 49 cases in each group. Both groups were treated with THA. 7 days after operation， control group was given routine anti-osteoporosis treatment [Gaierqi D tablets （containing 600 mg calcium/vitamin D3 125 IU in each tablet）， p.o.， one tablet/time， once a day； Calcitriol soft capsules （25 μg each pill， p.o.， 2 pills/time， once a day）]. Observation group was additionally given Alendronate sodium tablets （10 mg/time， once a day） on the basis of control group. Both groups were treated for consecutive 3 months. The hip function excellent rate was evaluated by using Harris scoring system at 7 days， 3 months and 6 months after operation. The periprosthetic 7 cases of egion interest （ROI1-7） BMD were detected and compared between 2 groups. RESULTS： The excellent rate of hip joint function in the control group were 16.33％， 40.82％， 69.39％ 7 days， 3 months， 6 months after operation， respectively； those of observation group were 17.78％， 73.33％， 88.89％ respectively. There was no statistical significance in the excellent rates of hip joint function between 2 groups 7 days after operation （P＞0.05）. The excellent rate of hip joint function in observation group was higher than control group 3 months and 6 months after operation （P＜0.05）. There was no significant difference in periprosthetic BMD between 2 groups 7 days after operation （P＞0.05）. Compared with 7 days after operation， BMD of ROI1， ROI6 and ROI7 in 2 groups were decreased gradually 3 months and 6 months after operation （P＜0.05 or P＜0.01）. BMD of ROI2， ROI3 and ROI5 decreased first and then increased （P＜0.05 or P＜0.01）. There was no significant change in BMD of ROI4 （P＞0.05）. There was no significant difference in BMD of each area between 2 groups 3 months after operation （P＞0.05）. BMD of ROI1， ROI2， ROI3， ROI5， ROI6 and ROI7 in observation group were significantly higher than control group 6 months after operation （P＜0.05 or P＜0.01）. CONCLUSIONS： THA combined with Alendronate sodium tablets and conventional anti-osteoporosis treatment can improve the excellent rate of hip joint function in patients with femoral neck fracture and the level of periprosthetic BMD.