Idiopathic orbital inflammatory pseudotumor(IOIP) is a common orbital disease.It is a nonspecific inflammatory process,and the etiology is still unknown.IOIP occurs at any position of orbit.The clinical manifestation varies according to the anatomic involvement and the degree of inflammation progress.IOIP can clinically mimic many other orbital diseases,especially serious type of this disease can present similar clinical characteristics as the malignant tumor,so it is comprehensive to make a clinical diagnosis.Currently,the diagnosis of IOIP is allowed based on the differentiation from an exclusion of other diseases by a thorough medical history and clinical manifestations,and then acquire some assistant information by radiologic evaluation and laboratory tests and observe the response to steroid treatment.The final diagnosis still requires histopathological examination.