Objective To observe the effect of ultrasound guided continuous femoral nerve block combined with single local infiltration anesthesia of hip joint capsule on the analgesia before hip replacement in the elderly and its influence on stress indicators and pain mediators.Methods A total of 98 elderly patients who underwent hip replacement in our hospital from January 2018 to March 2022 were selected and divided into the two groups by random number method. The control group received a single local infiltration anesthesia of the hip joint capsule, while the observation group received ultrasound-guided continuous femoral nerve block combined with a single local infiltration anesthesia of the hip joint capsule. The surgical conditions (sensory block time, postoperative ambulation time, pain recovery time, etc.) were compared between the two groups, and the visual analog (VAS) score was used to evaluate the pain degree of the two groups at different times after the operation, and the two groups were recorded from 0 to 24 hours after the operation., Opioid doses within 24-48h, and differences in stress indicators ［blood glucose, C-reactive protein (CRP)］ and pain mediators ［5-hydroxytryptamine (5-HT), substance P (SP)］ before and after surgery were detected between the two groups.Results The recovery time of sensory block and pain in the observation group was longer than that in the control group, and the time of getting out of bed and hospitalization after operation was shorter than that in the control group. The VAS scores at rest and exercise at 6h, 12h, 24h and 48h after operation were lower than those in the control group. The time of awakening and laryngeal tube removal had no statistical significance compared with the control group (P＞0.05). Before surgery, there was no statistical significance in the comparison of stress indicators and pain mediators between the two groups (P＞0.05). At 48 hours after operation, blood glucose, CRP, 5-HT and SP in the observation group were higher than those before operation, and the above indexes in the observation group were lower than those in the control group at 48 hours after operation, with statistical significance (P＜0.05). The dose of opioids in the observation group was significantly lower than that in the control group within 0-24h and 24-48h after operation, with statistical significance (P＜0.05). No anesthesia-related adverse reactions occurred in 98 patients after operation.Conclusion Ultrasound-guided continuous femoral nerve block combined with a single session of local infiltration of the hip joint capsule can reduce the stress response and release of pain substances in elderly patients undergoing hip arthroplasty, thereby reducing postoperative pain, reducing the application of opioids, and promoting Postoperative recovery