Objective To study the changes of serum procalcitonin (PCT) in the patients with simple brain trauma and its relationships with injury of severity, complications and outcome of injury.Methods A total of 120 patients with simple brain trauma were evaluated in a prospective observational study.The serum levels of procalcitonin and C-reactive protein were measured 1,2,3,5,7 and 10 days after the admission.During the following ten days after admission,the clinical data of patients with simple brain trauma were recorded,and also the patients with 28-day survival were followed up.Another 30 healthy subjects were enrolled in normal group for comparison. Results In different periods after trauma,the PCT levels in brain injury patients with different degree of injury severity were significantly different ( P ＜ 0.05 ).During the first two days after admission,there were no significant differences in serum PCT levels between non-infection group and infection group,but significant differences were found between two groups on the 3rd,5th,7th and 10th days ( P ＜ 0.05 ).Kaplan-Meier survival analysis showed the 28 days survival between the group with high PCT level and the group with lower PCT level was statistically significant ( P ＜0.05 ). Conclusions Poor outcomes and complications such as infection were often occurred in simple brain trauma patients with initially high PCT.The frequent determination of serum PCT levels is a useful approach to the judgment of injury severity and proguosis in patients with simple brain trauma.