Abstract: Objective To study the pathological features of sclerotic synovial sarcoma（SS） and its diagnosis and differential diagnosis. Methods Clinical manifestations,pathological morphology,immunohistochemical staining,special staining and specific changes in cytogenetics of leg sclerotic SS in a patient were analyzed with the related literature reviewed. Results This case of leg sclerotic SS was first reported.The patient was 29-year-old with a 13-year history of left leg sclerotic SS.A large number of irregular trabecular collagens were found in the tumor with a rarefaction of tumor cells and spindle cells around the collagens,some of which were epithelial cells growing around the small blood vessels,and calcification and ossification in certain areas of the tumor.Immunohistochemical staining showed that the tumor was positive for EMA（epithelial memberane antigen）,CK（cytokeratin）,vimentin,Bcl-2,CD99 and negative for CD31,CD34,desmin and SMA.P53 positive cells accounted for 50%-75%.Reticulum fibers in sclerotic interstitial area were positively stained with AB while PAS staining was negative.FISH showed SS18（18q11.2） chromosome translocation. Conclusion Sclerotic SS is an extremely rare type of synovial sarcoma.Its differential diagnosis can be made with immunohistochemical staining and molecular detection from parosteal osteosarcoma,myositis ossificans,fibrosarcoma,desmoplastic fibroma of bone and hemangiopericytoma.