Objective: To investigate the effects of supine position direct anterior approach (DAA) and lateral position direct lateral approach (DLA) on hip function, balance function and gait parameters in patients undergoing primary total hip arthroplasty (THA). Methods: 97 patients with primary THA admitted to our hospital from February 2018 to October 2019 selected, and were divided into group A (n=47) and group B (n=50) according to the different ways of approach, group A was given lateral position DLA, group B was given supine position DAA. The hip function, imaging parameters, balance function and gait parameters were compared between the two groups, and the incidence of postoperative complications was recorded. Results: 1 week, 1 month, 3 months and 6 months after operation, Harris score (HHS) and Berg Balance Scale score (BBS) of hip joint of the two groups showed an increasing trend, and group B was higher than group A (P<0.05). The operation time of group B was longer than that of group A, the intraoperative hemorrhage was less than that of group A, the incision length and time of first walking out of bed were shorter than those of group A (P<0.05). 3 months and 6 months after operation, the step frequency, step speed and step length of the two groups were increased in turn, and group B was higher than group A (P<0.05). There was no difference in the incidence of complications between the two groups (P>0.05). Comparison of acetabular abduction angle and anteversion angle between the two groups 6 months after operation showed no differences (P>0.05). Conclusion: Compared with lateral position DLA, the patients with primary THA are given supine position DAA, it can obtain the same surgical effect, and can improve the hip joint function, balance function and gait parameters, and the safety is guaranteed. [ABSTRACT FROM AUTHOR]