Objective The aim of this study was to investigate the effects of different doses of dexmedeto⁃ midine on inflammatory response，immune function and brain function in patients with sepsis⁃associated encepha⁃ lopathy（SAE）. Methods A total of 60 patients with SAE were enrolled and randomly divided into L，M，and H groups according to the different dose of dexmedetomidine. The above three groups were given dexmedetomidine 0.2，0.4 and 0.6 μg/（kg·h）respectively. Inflammatory factors（TNF⁃α and IL⁃6），immune function（CD4+ ，CD8+ and CD4+ /CD8+ ）and brain function（SjvO2，Da⁃jvO2，CERO2 and S100β）before administration（T0），and 12 h （T1 ），24 h（T2 ），72 h（T3 ）after treatment were recorded and compared. Incidence of adverse reactions，length of stay in the ICU and mortality were also recorded. Results Inflammatory response and immune function：the inflamma⁃ tory response and immune function of group H were significantly improved when comparing with group L at T1； Group H were better than the other two groups at T2 and T3 in inflammatory response and immune function；Group H > group M > group L in reducing inflammation and improving immune suppression at T3（P < 0.05）. Brain function：the cerebral oxygen index of group H was significantly better than that in group L and M at T2 and T3，and the S100β at T3 was significantly lower than the other two groups（P < 0.05）. There was no significant difference in the incidence of bradycardia，hypotension，length of ICU stay and mortality among the three groups（P > 0.05）. Conclusion Dexmedetomidine could reduce inflammation and immunosuppression ，improve cerebral oxygen metabolism and brain function with 0.6 μg/（kg·h）treatment. It did not increase the incidence of adverse reactions and its effects would be more and more significant with the increase of dexmedetomidine dose.