Objective: To investigate the clinicopathological and molecular genetics features of synovial sarcoma (SS) of the orbit. Methods: We retrospectively reviewed 10 published cases of primary SS of the orbit, along with 1 case of primary SS of the orbit confirmed by pathology who was admitted to the ophthalmology department of Eye & ENT Hospital of Fudan University in October 2020. The clinical data, radiological findings,morphology, immunophenotype and genetic characteristics of the cases were analyzed. Results: Our case was a 53-year-old woman with an SS in the right orbit, which had recurred multiple times. Histopathologic examination showed a primitive tumor composed of spindled and ovoid cells. Focal infiltration was observed in adjacent structures, such as the sub-conjunctiva, scleral surface, optic nerve sheath, muscle, and fibro-fatty tissue. Immunohistochemistry showed positivity for vimentin, calponin, CD99, and Bcl-2 and loss of INI-1expression, which is typical of SS. Fluorescence in situ hybridization (FISH) showed the (X;18)translocation in the tumor cells. The analysis included 2 males and 9 females aged between 1 and 53 years old (mean: 22 years; median: 24 years). Among the SS cases, 6 left eyes and 5 right eyes (all monocular cases)were affected. Symptoms had been present from 1 week to 13 years in the case from our hospital, while in 5 cases, symptoms had been present for at least 3 years. Common clinical features of the patients included proptosis or globe displacement, decreased vision, and pain. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed an ovoid mass with heterogenous enhancement and a cystic appearance,which was probably attributable to hemorrhage or necrosis. Of these 11 cases, 7 cases were biphasic SS,4 were monophasic fibrous SS, and 2 were poorly differentiated in monophasic SS. Immunohistochemistry revealed positivity for pan-cytokeratin (CKpan), CK7, CK19, vimentin, cluster of differentiation 99 (CD99),B-cell lymphoma 2 (Bcl-2), calponin and transducin-like enhancer protein 1 (TLE1). Conclusion: Primary SS of the orbit is extremely rare and needs to be distinguished from other spindle cell tumors of orbital soft tissue. The SS diagnosis is based on the presence of the t(X;18) (p11; q11) translocation, which results in an SYT-SSX fusion gene.