Abstract: Objective To investigate the value of cerebral state index (CSI) in monitoring the consciousness state of patients with brain trauma.Methods The consciousness sates of 218 patients with craniocerebral trauma were assessed by three experienced specialists by Glasgow Coma Scale (GCS),and the CSI of the patients were measured by Cerebral State Monitor.Correlation between GCS and CSI as well as the distribution of CSI in various consciousness defined by GCS were discussed.The predictive value of CSI in discriminating different conscious states of the patients was also analyzed.Results The Cochran Q test showed that there was a consistency of the GCS judged by three specialists (P ＞ 0.05),and the CSI of the patients was positively correlated with the GCS (r=0.819,P＜0.001).A gradual decrease in the CSI was found across categories of the various consciousness states,including sobriety,somnolence,confusion,light coma,coma in moderate depth and deep coma.The receiver operating characteristic curve (ROC) analysis showed that CSI could significantly discriminate the different consciousness states of the patients (P ＜0.001).The area under the curve (AUC) for the consciousness was 0.995 for deep coma,0.984 for sobriety,0.815 for coma in moderate depth,0.769 for somnolence,0.768 for light coma and 0.695 for confusion,respectively.Conclusion CSI can be used to monitor the severity of craniocerebral trauma.