Objective To observe the expression and distribution of insulin-like growth factor-1 receptor (IGF-1R) in orbital adipose tissues of patients with thyroid-associated ophthalmopathy (TAO), and to explore the effect of insulin-like growth factor-1 (IGF-1) on the proliferation and differentiation of orbital preadipocytes. Methods We harvested the orbital adipose tissues from 6 patients with TAO (TAO group) and 5 controls (control group); the patients were treated in Changzheng Hospital, Second Military Medical University from Sep. 2014 to Jan. 2015. The expression and distribution of IGF-1R in the orbital adipose tissues were examined by Western blotting analysis, real-time PCR and immunohistochemistry. The orbital preadipocytes were extracted in two groups, and the effects of different concentrations of IGF-1 (0 nmol/L, 1 nmol/L, 5 nmol/L, 10 nmol/L, and 20 nmol/L) on cell proliferation were examined by CCK8. The differentiation of cells and the expression of IGF-1R were observed by oil red O staining and Western blotting; the effect of different concentrations of IGF-1 (0 nmol/L, 1 nmol/L, 5 nmol/L, 10 nmol/L, and 20 nmol/L) on preadipocyte differentiation was detected by real-time PCR. Results The expressions of IGF-1R protein and mRNA in orbital adipose tissues in TAO group were significantly higher than those in the control group (P<0.01). The proliferation of orbital preadipocytes was promoted in both groups, and the cell proliferation in TAO group was significantly higher than that in control group when treated with 1-20 nmol/L IGF-1 (P<0.05, P<0.01). The expression of IGF-1R in the TAO group was significantly higher than that in the control group before and after differentiation. Compared with IGF-1 absent group, 1-20 nmol/L IGF-1 significantly promoted the expression of PPARγ mRNA in orbital preadipocytes in TAO group (P<0.01). Oil red O staining results showed that the lipid droplet synthesis was significantly increased with the increase of IGF-1 concentration (P<0.05, P<0.01). Conclusion IGF-1R is highly expressed in the adipose tissue and preadipocytes in patients with TAO, and IGF-1 can promote the proliferation and differentiation of preadipocytes in patients with TAO.