Abstract: Objective To study the value of MRI imaging in the diagnosis of invasive pituitary adenoma. Methods Review and analysis the MRI sign in the 32 patients of invasive pituitary adenoma comfirmed by operation and pathology. Results The following signs have been found to represent accurate criteria for invasive pituitary adenoma:①Adenoma exceeded the lateral intercarotid(ICA) line;②Cavernous sirus lateral venous compartments disappeared;③Occlusion of three or more cavernous sinus venous compartments disappeared; ④Percentage of encasement of the intracavemous ICA higher than 50% was crossed. Conclusions No trauma, no bone shadow, higher soft tissue resolution, clear anatomy background and 3D imaging act as MRI's virtue, which have became the capital examination means of preoperative diagnosis of infestation vascular tumor.