Objective:To observe the effect of early temperature control on the prognosis of brain injury patients after severe carbon monoxide poisoning (COP).Methods:A total of 277 patients hospitalized with severe COP were randomly divided into a fever group ( n=78), a normal temperature group ( n=113) and a mild hypothermia group ( n=86). All were given hyperbaric oxygen therapy and any necessary supportive treatment. The mild hypothermia group were kept in a room at 34 to 35℃. Evaluation was with the Glasgow Coma Scale (GCS), version II of the Acute Physiology and Chronic Health Evaluation (APACHE), the Hasegawa dementia scale (HDS) and the mini mental state examination (MMSE). The incidence of delayed encephalopathy (DEACMP) and mortality were compared among the three groups. The bispectral index (BIS) and neuron-specific enolase (NSE) levels were correlated with DEACMP. Results:After the treatments, improvement was observed in multiple indexes of all three groups compared with before the treatment. Compared with the fever group, the average GCS of the mild hypothermia group was significantly higher on the 2nd, 4th, 8th and 31st day after the intervention. It was significantly higher than the normal temperature group′s averages on the 4th, 8th and 31st day. The average APACHE scores of the normal temperature and the mild hypothermia groups were significantly lower than the fever group′s average, with that of the mild hypothermia group significantly lower than that of the normal group. The average HDS scores of the normal temperature and mild hypothermia groups were significantly higher than the fever group′s average, with that of the mild hypothermia group significantly higher than that of the normal group. The average MMSE score of the mild hypothermia group was significantly improved after 7 days, one month and three months of treatment. That of the normal group showed significant improvement after one and three months, but the mild hypothermia group′s averages were superior. Compared with the fever group, the average BIS score of the mild hypothermia group was significantly better after one, three and seven days, and one month. This was true for the normal group beyond three days after the intervention. The average NSE concentration of the normal group after 7 days and one month was significantly lower than that of the fever group. For the mild hypothermia group this was true after only 3 days. Compared with the other two groups, the average coma time, incidence of DEACMP and nervous system injury were significantly lower in the hypothermia group. The average GCS, BIS and NSE values were closely related to the occurrence of DEACMP.Conclusions:Early temperature control can significantly reduce the severity of brain injury after COP and reduce the incidence of neurological sequelae. Early dynamic detection of GCS, NSE concentration and BIS is of great significance for predicting the incidence of DEACMP.