Objective To investigate the relationship between the changes of regional cerebral oxygen saturation (rSO₂) and postoperative delirium in the elderly after general anesthesia. Methods A total of 76 elderly patients receiving spinal surgery under general anesthesia in our hospital from January 2017 to January 2018 were enrolled in this study. After entering the operation room, the patients were monitored for rSO₂ continuously. rSO₂, heart rate (HR) and mean arterial pressure (MAP) were recorded before anesthesia induction (T0), after tracheal intubation (T1), at the beginning of (T2), in 1h(T3) and 3h(T4) after, and at the end of operation (T5). With the rSO₂ value at T0 as the baseline value, the mean (rSO₂), minimum (rSO_2min) and maximum descendence (ΔrSO_2max) of rSO₂ from T0 to T5 were calculated. Consciousness disorder test (CAM) was applied for the cognitive status of postoperative patients, and they were divided into postoperative delirium group (POD group, n=14) and non-postoperative delirium group (NPOD group, n=62). SPSS statistics 18.0 was used to analyze the data. t test, the analysis of variance of repeated measurement or pairwise comparison was employed for comparison. Results The incidence of POD was 18.4%(14/76) in this study. There were no significant differences in MAP and HR at T0 to T5 between the 2 groups (P>0.05). Though no obvious differences were seen in rSO₂ at T0-T3 between the 2 groups (P>0.05), the value was significantly decreased in the POD group than the NPOD group at T4 and T5 (P<0.05). The POD group had significantly higher ΔrSO_2max [(0.09±0.04)% vs (0.05±0.02)%], and lower rSO₂ [(73.29±1.69)% vs (75.49±1.89)%], but no obviously difference in rSO_2min [(65.00±3.40)% vs (67.47±5.10)%, P>0.05] and baseline [(71.14±0.77)% vs (70.95±0.89)%, P>0.05] when compared with the NPOD group. Conclusion There is a significant correlation between the decrease of intraoperative rSO₂ and occurrence of POD. The monitoring of rSO₂ during operation can be used as an auxiliary means to predict the occurrence.