The objective of this study was to analyze the clinical features of brain trauma associated syndrome of inappropriate antidiuretic hormone secretion. A retrospective analysis was performed for the electrolytes and osmolality of blood and urine samples of brain injury patients, which have been collected in our department since last 20 years. Four cases of brain injury patients met the criteria of SIADH, and three of them were cured but one patient died. In conclusion, the pathogenesis and treatment of SIADH associated with brain injury are different from hyponatremia. Early diagnosis and treatment can reduce the morbidity and mortality of patients with traumatic brain injury.