Objective To investigate the effect of bispectral index (BIS) on the brain injury and prognosis in patients with diffuse axonal injury (DAI). Methods There are totally 47 patients who were admitted in the First People’s Hospital of Yancheng from January 2016 to september 2016. The BIS was continuously monitored for 12 h within the first 3 days after admission to hospital or 24 hours after stoppage of sedative. At the same time, the glasgow coma scale (GCS)was evaluated, the serum levels of NSE and S100 protein were determined, and the patients were followed up for three months. The correlations among BIS, GCS, NSE and S100, as well as the differences in GCS, NSE and S100 between different BIS groups were analyzed. The differences in BIS, GCS, NSE and S100 were compared between the poor and good prognosis groups.  Results BIS was positively correlated with GCS (r=0.626, P＜0.0014), whereas negatively correlated with NSE and S100 (r=-0.607, P＜0.001; r=-0.680, P＜0.001). GCS, NSE and S100 had significant differences in different BIS groups (all P＜0.001). Moreover, BIS, GCS, NSE and S100 were significantly different between patients with poor and good prognosis.Conclusion BIS is non-intrusive, easy to operate and allows for continuous monitoring. It is an objective index beneficial for early stage evaluation and prognosis of DAI.