Abstract: Objective To investigate the clinicopathologic features，immunophenotyping， differential diagnoses， treatment and prognosis of myeloid sarcoma（MS）. Methods The clinical and pathologic data of 6 cases of MS were reviewed. HE stain，immunohistochemistry stain by EnVision method and bone marrow slides examination were carried out. The followed up information was available in all patients. Results There were 3 males and 3 females. The age ranged from 23 to 66 years. The sites of involvement included small intestine， palate， palm of the hand， colon， lung and cervix.The tumor cells were widespread infiltration，diffused distribution with no adhesion each other； tumor cells were middle size， little cytoplasm and large nucleolus. Nucleolus were round and orbicular-ovate. Chromatin was exquisite and uniform distribution; nucleolus was clear with different sizes in 2 cases. Some eosinophilic granulocytes were visible. Immunohistochemical study showed that cases were positive for MPO， CD43， CD117， CD68-KP1， CD13， CD15 and lysozyme. According to histopathology feature and immunohistochemical result， the 6 patients were granulocytic sarcoma. During the follow-up， 3 cases with AML died at 5， 6， 11months after diagnosis. Other three patients survived. Conclusion MS is a scarce malignant tumor that is myeloid cells morphology and immunophenotype characters. The diagnosis should be based on tissue morphology and immunohistochemistry observation.