Abstract： Objective To investigate the effects of ultrasound-guided femoral nerve combined with sciatic nerve block anesthe-sia on the safety of anesthesia and plasma cortisol in elderly patients with lower limb fractures undergoing surgical treatment.Methods 88 elderly patients with lower extremity fracture admitted to our hospital from October 2020 to November 2022 were divided into two groups by random number table method(n=44).Both groups underwent surgical treatment for lower extremity fracture.The control group and observation group were given combined epidural anesthesia and ultrasound-guided femoral nerve combined sciatic nerve block anesthesia,respectively.The relevant clinical indicators,MAP and HR of T0,T1 and T2,pain(VAS score)at 2h,6h,12h and 24h after surgery and perioperative plasma cortisol levels were compared between the two groups.Results Compared with the control group,the effect of sensory and motor nerve block,postoperative urination and lower limb movement recovery time in observation group were shorter(P<0.05).Compared with T0,MAP level decreased and HR level increased at T1 and T2,and compared with control group,MAP level was lower and HR level was higher in observation group(P<0.05).Compared with the control group,VAS scores in the ob-servation group were lower at 2 h,6 h,12 h and 24 h after surgery(P<0.05).Compared with before anesthesia,plasma cortisol levels in both groups were increased 2 hours after surgery and 3 days after surgery,but compared with the control group,the increase of plasma cortisol levels in the observation group was smaller(P<0.05).Conclusion The use of ultrasound-guided femoral nerve combined with sciatic nerve block anesthesia for elderly patients with lower extremity fractures undergoing surgery can have a good anesthetic effect,lit-tle impact on the hemodynamic level of patients,higher safety,and positive significance in stabilizing the perioperative plasma cortisol level and reducing the postoperative pain of patients.