Objective To investigate dynamic changes of serum Tau proteins and their correlation with cognitive dysfunction in patients with acute traumatic brain injury (TBI).Methods A total of 95 patients with acute TBI were retrospectively studied by case-control study.There were 61 males and 34 females,with age of 16-65 years [(40.7 ± 13.6)years].The Glasgow coma scale (GCS) was 3-8 points in 9 patients,9-12 points in 11,and 13-15 points in 75.A total of 30 healthy physical examinees were recruited as control group.The levels of Tau proteins were measured at days 1,3,5,7 and 14 after TBI.The cognitive dysfunction was evaluated by the Montreal Cognitive Assessment (MoCA) score at 6 months after injury.The correlation between Tau protein levels at different time points and MoCA was determined.Results The serum Tau proteins of TBI group was significantly higher than that of control group at all time points (P ＜ 0.05).In TBI group,39 (41％) out of 95 patients developed cognitive dysfunction assessed by MoCA scale.The main manifestations of cognitive dysfunction were the defects in visual spatial and acting function,delayed memory,language,abstract,attention and calculation,with statistical significance compared with control group (allP ＜ 0.05).The serum Tau proteins of patients with cognitive dysfunction were significantly higher than those without cognitive dysfunction at all time points after TBI (P ＜ 0.05).Tau proteins at days 1,3,5 after TBI was significantly correlated with cognitive dysfunction at 6 months after TBI (P ＜ 0.05).Conclusions The levels of serum Tau proteins show a significant increase after TBI,the early changes of which are statistically related to cognitive dysfunction.The early changes of serum Tau protein after TBI can be used as a reliable biomarker for early prediction of cognitive function prognosis.