Traumatic brain injury is a disease with high incidence, disability, and mortality rates. More and more studies have found that traumatic brain injury can cause gastrointestinal symptoms and interact with gut microbiota. The gut microbiota affects the progression and prognosis of TBI through the brain gut axis, involving multiple pathways such as neurology, endocrinology, and immunity. However, the mechanism of the brain gut axis has not been thoroughly studied. This review will summarize and analyze the research progress on the bidirectional regulation mechanism of the brain gut axis.