Objective To investigate the effects of different anesthesia depths on intraoperative glucose and lactate and postoperative cognitive function in elderly patients undergoing supratentorial tumor resection. Methods Totally 120 elderly patients undergoing supratentorial tumor resection admitted to 903 Hospital and Sichuan Provincial Cancer Hospital from February 2017 to June 2019 were selected and divided into group A (n=40) with bispectral (BIS) index 30-39, group B (n=40) with BIS index 40-49, and group C (n=40) with BIS index 50-59. Blood samples were taken from radial artery and jugular venous bulb simultaneously before induction of anesthesia (T1), at the intubation (T2), during separation (T3), at removal (T4), and at the closure of dura (T5). Glucose extraction rate (GluER) and cerebral lactate production rate (LacPR) were measured. At D1, D3 and D7, mini-mental state examination (MMSE) was adopted to evaluate cognitive function, and the serum S100β and neuron-specific enolase (NSE) were measured. Data were analyzed using SPSS statistics 19.0. Analysis of variance was used between multiple groups, and comparisons between the two groups were performed using LSD-t test. Results Compared with T1, GluER was significantly reduced at each time point after induction in group A and group C (all P<0.05), while GluER in group B had no difference before and after induction (all P>0.05). Compared with T1, the LacPR of group B decreased gradually from T2 to T5 (P<0.05), but there was no difference in the LacPR of group A and C (both P>0.05). At D1, D3 and D7, MMSE scores of group B were significantly higher than those of the other two groups (P<0.05), while serum S100β and NSE of the group B was significantly lower than those of the other two groups (P<0.05). Conclusion The anesthesia depth with BIS index 40-49 can control cerebral metabolism in the elderly patients undergoing supratentorial tumor resection, maintain blood glucose balance, and reduce LacPR, thereby improving postoperative cognitive function.