Objective To compare the clinical outcomes of direct anterior approach（DAA）in lateral position and modified anterolateral approach in supine position （MAASP）in unilateral total hip replacement. Methods 76 patients who were to undergo unilateral total hip replacement were enrolled，and they were randomly divided into group A and group B（38 cases each）. Total hip replacement with DAA in lateral position was performed in group A，while total hip replacement with MAASP was performed in group B. The operative indexes（operation time，intraoperative hemorrhage，incision length，first time out of bed activity time，postoperative hospital stay time），postoperative pain levels at 1，3 d and 7 d after operation，acetabular anteversion and lower limb length difference after operation，hip function scores at 3，6 months and 1 year after operation and complications with in 1 year were compared between the two groups. Results The operation time，incision length，the first time of getting out of bed after operation and the time of hospitalization in group B were shorter than those in group A（P < 0.05）， and the amount of intraoperative bleeding was less than that in group A（P < 0.05）. The pain scores at 3 d and 7 d after operation were lower than those at 1 d after operation in both groups（P < 0.05），and the pain scores at 7 d after surgery were lower than those at 3 d after operation（P < 0.05），and the pain scores at 1，3 d and 7 d after operation in group B were lower than those in group A（P < 0.05）. There were no statistical differences in hip joint function scores at 3 months，6 months and 1 year after operation and complications within 1 year between the two groups （P > 0.05）. Conclusion DAA in lateral position and MAASP can both increase hip joint function recovery，but the latter is less traumatic，recovers faster，and has less postoperative pain.