Objective To investigate the causes of exophthalmos due to orbital disease,including its classification and distribution.Methods It was a retrospective case series study.Data was collected on all cases of exophthalmos,excluding cases with incomplete data and unclear diagnoses.Medical records from 583 patients were retrospectively analyzed for gender,age,causes of exophthalmos,clinical manifestations,and laboratory examination.Number were counted and expressed with percentage.Results Causes that resulted in exophthalmos can be divided into 5 categories:tumor (58.3％),thyroid-associated ophthalmopathy (21.4％),inflammatory disease (17.2％),trauma (2.7％),and genetic and developmental disorders (0.3％).Tumors can be further divided into those originating in intraorbital cavities (72.9％),paranasal sinus tumors spreading into orbital cavities (18.5％),hematopoietic tumors (4.1％),brain tumors spreading into orbital cavities (3.2％),intraocular tumors spreading into orbital cavities (0.6％) and metastatic carcinoma (0.6％).Common causes of exophthalmos were thyroid-associated ophthalmopathy (21.4％),cavernous hemangioma (11.2％),inflammatory pseudotumor (10.3％),benign meningiomas (6.5％),venous angioma (6.0％),orbital cellulitis (5.3％),dermoid and epidermoid cysts (4.6％),nerve sheath tumors (3.6％),squamous cell carcinoma (2.9％),pleomorphic adenoma (2.7％),etc.The causes of exophthalmos in children included hemangioma,orbital cellulitis,dermoid and epidermoid cysts,meningioma,inflammatory pseudotumor,schwannoma,glioma,neurofibroma,thyroid eye disease,rhabdomyosarcoma,etc.Conclusion Exophthalmos can be caused by a variety of orbital diseases.The causes of unilateral exophthalmos are tumor,thyroid-associated ophthalmopathy,inflammation,etc.Bilateral exophthalmos is more commonly caused by thyroid eye disease.The causes of exophthalmos for adults and children are different,in which hemangioma is more common in children and thyroid-associated ophthalmopathy is more common in adults.