Traumatic brain injury (TBI) is a common clinical disease in neurosurgery, among which the mortality rate of severe and extra-severe TBI is very high. The primary or secondary TBI can easily lead to severe damage to the structure and function of the brain, some patients may develop into brain death. In addition, TBI patients are usually complicated with multiple injuries, so the accuracy and reliability of brain death diagnosis for TBI patients are increasingly required in clinic. Most countries in the world mainly rely on clinical diagnosis of brain death combined with assistive technology, which can further improve the accuracy of brain death diagnosis. In this paper, the concept, development and several assistive techniques of brain death diagnosis are summarized, so as to provide reference for the accurate diagnosis of brain death after TBI.