Thyroid-associated ophthalmopathy (TAO) is an organ-specific autoimmune disease closely related to thyroid disease, which leads the incidence of orbital disease in adults and is the most common cause of diffuse toxic goiter (Graves disease, GD). The clinical manifestations of TAO are complex and varied. In severe cases, it may seriously impair visual function, affect daily life, and even cause corneal ulceration, perforation, and blindness. Therefore, a reasonable and effective treatment plan should be chosen according to the degree of TAO. IBI311 is a fully human monoclonal insulin-like growth factor-1 receptor inhibitory antibody. It has binding activity against IGF-1R positive cells, can block the binding of IGF-1 and IGF-2 to IGF-1R, and has a dose-dependent effect. It can inhibit the proliferation of HT29 cells caused by the activation of the IGF-1R signaling pathway. Meanwhile, it can dose-dependently inhibit the proliferation of orbital fibroblasts and the secretion of hyaluronic acid (HA) in patients with TAO. However, there are still significant gaps in the existing research evidence: There is a lack of reports on the efficacy and safety of IBI311 in inactive moderate to severe TAO patients. The aim of this clinical study is to: 1. To evaluate the efficacy of IBI311 treatment in patients with inactive moderate to severe TAO. 2. To observe the safety of IBI311 treatment in patients with inactive moderate to severe TAO.