Abstract： Objective:To explore the clinical effects of hyperbaric oxygen as an adjuvant therapy on delayed encephalopathy after acute carbon monoxide poisoning（DEACMP）.Methods:A total of 136 DEACMP patients admitted to Linyin Central Hospital from September 2018 to March 2020 were selected and randomly divided into control group and observation group，with 68 cases per group. Patients in the control group were given symptomatic treatments such as improving cerebral circulation and nourishing nerves，and patients in the observation group were given hyperbaric oxygen as an adjuvant therapy on the basis of the treatment in the control group. The clinical efficacy，central neuro-specific protein S100β，neuron-specific enolase（NSE）levels，and neurological function recovery of the patients in the two groups were compared.Results:The total effective rate of the observation group was higher than that of the control group（88.24% > 67.65%），with statistically significant difference（ P<0.05）. After treatment，the scores of mini-mental state examination scale（MMSE），neurological functional deficit scale（NFDS），and Barthel index（BI）of the patients in the two groups were significantly improved compared with those before treatment，and the improvements in the observation group were better than those in the control group，and the differences were statistically significant（ P<0.05）；the S100β and NSE levels of patients in the two groups were significantly decreased than those before treatment，and the two levels in the observation group were much lower than those in the control group，with statistically significant differences（ P<0.05）；while there was no significant difference in the occurrence of adverse reactions between the two groups（ P>0.05）. Conclusion:Hyperbaric oxygen as an adjuvant treatment of DEACMP patients can help to reduce neuronal damage and promote nerve cell function recovery，thus better improving the cognitive and daily living abilities of patients and facilitating their recovery.