【Abstract】 Objective To compare the effect general anesthesia combined with femoral nerve block on perioperative diaphragmatic function in patients undergoing knee arthroscopic surgery. Methods 98 patients (110 enrolled and 12 excluded) undergoing elective knee arthroscopic surgery, aged 25-65y, with the American Society of Anesthesiologists physical status Ⅰ or Ⅱ , randomly divided into two groups according to the random number table method: general anesthesia combined with femoral nerve block group(group GANB, n=53) and general anesthesia group (group GA, n=45). All patients receiced combined intravenous and inhalation anesthesia, and patients in group group GANB completed ultrasound-guided femoral nerve block before anesthesia induction. The diaphragm excursion (DE) and diaphragmatic thickening fraction (DTF) were observed by ultrasound to evaluate the diaphragmatic function. The intraoperative medication, extubation time, postoperative numeric rating scale (NRS)scores and postoperative pulmonary complications in the two groups were observed and recorded. Results Postoperatively, the DE was significantly greater in the group GANB than in the group GA[(1.56±0.41)cm vs (1.33±0.35)cm, P 0.05]，while no difference was observed in DTF (P0.05). There was no significant difference in DE and DTF during the recovery period in both groups (both P 0.05). The intraoperative sufentanil dosage in the group GA was significantly higher than that in the group GANB [(32.44 ± 5.90) μg vs (19.43 ± 4.35) μg, P 0.05]. The total amount of muscle relaxant, muscle relaxant antagonist, operative time, extubation time, postoperative NRS scores, and postoperative pulmonary complications showed no significant differences between two groups(all P0.05). Conclusions Compared with general anesthesia, femoral nerve block combined with general anesthesia can improve postoperative diaphragm excursion and reduce the dosage of opioids in patients undergoing lower limb surgery, and it is a recommended anesthetic method for lower limb surgery.