Thyroid - associated ophthalmopathy(TAO)is a vision - threatening autoimmune disease. Patients usually suffer from proptosis，diplopia or strabismus. In severe cases，the optic nerve may be compressed，resulting in visual impairment or even blindness. Serum immunoglobulin G4(IgG4)is a specific antibody that is associated with a variety of autoimmune diseases. Current studies have found that some TAO patients have elevated serum IgG4 levels，and these patients tend to have more severe symptoms. In the occurrence and development of ophthalmopathy，IgG4 may induce orbital fibroblasts to generate hyaluronic acid and promote the production of autoantibodies. IgG4 may play a role in the pathogenesis of TAO alone or in combination with thyrotropin receptor antibodies. Studies have shown that serum IgG4 is related to the clinical activity and severity of TAO. High IgG4 may indicate that TAO is in the early stage of inflammatory activity，and timely intervention can slow down the progression of muscle lesions and orbital fibrosis. Therefore，this article reviewed the relevant literature to explore the relationship between serum IgG4 and thyroid-associated ophthalmopathy，with a view to earlier and more effective clinical management of patients with TAO.