Objective To analyze the clinical features of delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) and explore the risk factors for delayed encephalopathy (DE).Methods A retrospective analysis of 276 patients with acute CO poisoning treated by HBO between January 2016 and January 2019 was consecutively conducted. According to the occurrence of DE, they were divided into DE group and non DE group. A univariate analysis was done for the clinical features between the two groups, and Logistic regression analysis for risk factors of DE. Results 41 cases (149%) were in the DE group, and 235 cases (851%) were in nonDE group. The age of DE group was older (641±135 vs. 500±191, P=0014) than that of non DE group. The ratio of the poisoning caused by heating (878%, vs. 613%, P=0004) and the consciousness duration more than 10 hours (537%, vs 170%, P=0000) of DE group were higher than that of non DE group. Logistic regression analysis showed that elder ones (OR 1043, 95%CI 1018, 1069, P=0001) and longer time of consciousness (OR 4268, 95%CI 2094, 8701, P=0000) were independent risk factors of DE. Conclusion Older age and longer periods of consciousness are risk factors for DE and require more intervention. Earlier hyperbaric oxygen therapy may indicate better prognosis for CO patients.