Objective: The purpose of this study was to examine the effects of various depths of anesthesia monitored using Narcotrend on cognitive function in elderly patients after video-assisted thoracic surgery (VATS) lobectomy. Methods: A total of 73 elderly patients who underwent VATS lobectomy were selected and divided into a control group (n=36) and an observation group (n=37) using a random number table. Both groups received general anesthesia. The Narcotrend index (NTI) of the control group was maintained at 50-59 and that of the observation group was maintained at 30-39. Results: The heart period (HP) and mean arterial pressure (MAP) from both groups were decreased first, and then were increased during T(1)-T(5); the MAP levels at T(2), T(3) , and T(4) were lower in the observation group than in the control group (P < 0.05). The propofol dosage was higher and the awake to extubation time was greater in the observation group than in the control group (P < 0.05). The visual analogue scale (VAS) score was lower in the observation group than in the control group at 6 h and 12 h after surgery (P < 0.05). The left and right regional cerebral oxygen saturation (rSO(2)) at T(3) -T(4) was higher in the observation group and the cerebral oxygen extraction ratio (CERO(2)) was lower in the observation group than in the control group (P < 0.05). Conclusion: The anesthetic depth that maintained an NTI of 30-39 as monitored using Narcotrend could improve cerebral oxygen metabolism, inhibit the inflammatory reaction, and reduce the incidence of postoperative cognitive dysfunction (POCD) in patients after VATS lobectomy.