Objective: To explore the effects of pericapsular nerve group (PENG) and lateral femoral cutaneous nerve (LFCN) block with bupivacaine liposome (LB) on stress and cognitive function in elderly patients after total hip arthroplasty. Methods: According to different intervention methods, 100 elderly patients undergoing total hip arthroplasty were divided into observation group (n=50, PENG+LFCN block with LB) and control group (n=50, PENG+LFCN block with ropivacaine). The postoperative analgesia, stress response, cognitive function, recovery and adverse reactions were compared between the two groups. Results: At 12, 24 and 48 h after surgery, VAS scores under rest and motion states, and compression frequency of patient controlled intravenous analgesia (PCIA) in observation group were lower than those in control group (P<0.05). At 1 d after surgery, levels of cortisol (COR), adrenaline (E) and norepinephrine (NE) in observation group were lower than those in control group (P<0.05). At 3 and 7 d after surgery, scores of mini-mental state examination (MMSE) in observation group were higher than those in control group (P<0.05). The first leaving bed time and length of hospital stay in observation group were shorter than those in control group (P<0.05). Conclusion: Compared with ropivacaine, PENG+LFCN block with LB has better analgesic effect in elderly patients after total hip arthroplasty, which can alleviate postoperative stress response, protect cognitive function and promote recovery.