[abstract] objective to investigate the security of the elderly patients with unilateral lower limb after trauma surgery anesthesia. Methods using a computer random coding, random draw 60 patients aged 80 ~ 99 - year - old orthopaedic surgery patients were randomly divided into nerve block group (N group) lumbar hemp and light weight waist hemp group (S group ), N group line set of lumbar plexus and sciatic nerve block anesthesia, S group lumbar hemp lines of light specific gravity, record before anesthesia and anesthesia after 1 min, 3 min, 5 min, 10 min, 15 min, 30 min, 1 h, 2 h, at the end of surgery in patients with Mean arterial pressure（Mean arterial pressure, MAP), Heart rate（Heart rate, HR), Blood oxygen saturation（Blood oxygen saturation, SPO2); Records of two groups of local anesthetics dosage effect time, block anesthesia, perfect time, adjuvant, sensory block plane; Observed two groups of anesthetic effect, postoperative complications and side effects. Results N group 10 min after anesthesia, MAP、HR、SPO2 respectively155.514.5、84.56.5,、98.51.5, (P > 0.05); S group 10 min after anesthesia, MAP、HR、SPO2 respectively 98.510.5, 98.54.5, 98.51.5, (P < 0.05); S groupMAP comparison group and N group P < 0.05. HR is compared between two groups (P > 0.05). Ngroup after anesthesia SPO2 compared with preoperative P < 0.01, after anesthesia Sgroup SPO2 compared with preoperative P < 0.05, compared between the two groups, P > 0.05. S group, the incidence of intraoperative hypotension and the incidence rate of postoperative shivering, nausea, vomiting, increased (P < 0.05, P < 0.01). Conclusion lumbar plexus and sciatic nerve block anaesthesia safer than lumbar hemp light specific gravity, hemodynamics in the elderly patients with unilateral lower limb surgery patients more smoothly, fewer complications, lumbar plexus and sciatic nerve block anesthesia can be used as a senile patients with lower extremity surgery is not suitable for lumbar hemp and reluctant to one general at the time of anesthesia method.