Objective To explore the effect of core muscle activity on lower limb strength and quality of life in elderly patients with femoral neck fracture after total hip arthroplasty. Methods From January 2016 to December 2018, 75 elderly patients with femoral neck fracture according to the inclusion criteria were selected . The patients were randomly divided into the control group (37 cases) and the observation group (38 cases), in which the traditional rehabilitation program was used in the control group , On the basis of the traditional rehabilitation ,the core muscle activity were added in the observation group. Results ① There was no significant difference in sex, age, side, BMI and fracture type between the two groups (P > 0.05). ② 12 weeks after operation, the step length, pace and Harris score of the observation group were better than those of the control group, the difference was tatistically significant (P < 0.01). ③ 4 weeks after operation, the Barthel score in the control group was lower than that before injury, and the observation group was better than the control group (P < 0.01). ④12 weeks after operation ,the Barthel score of the two groups was significantly better than that of the control group (P < 0.01). Conclusions Core muscle group activity could increase muscle strength, improve balance function, and improve the quality of life of elderly patients with femoral neck fracture after total hip arthroplasty.