Abstract: Objective To evaluate the expression level and binding affinity glucocorticoid receptor （GR） in endogenous Cushing’s syndrome patients. Methods The patients of endogenous Cushing’s syndrome were enrolled in the department of endocrinology in West China Hospital of Sichuan University, and age- and sex-matched healthy volunteers were studied as control group. The expression level and binding affinity of GR in peripheral blood mononuclear cells (PBMCs) were examined by flow cytometry. The differences between the two groups were compared, and the correlations of GR level and affinity to serum cortisol concentration or 24 h urine free cortisol were also analyzed. Results There were 17 Cushing’s syndrome patients and 17 healthy volunteers. The expression level and binding affinity of GR in Cushing’s syndrome patients were 11.9±3.1 and 6.6±2.6, while the values of normal controls were 20.6±3.3 and 9.9±3.2. A significant decrease in GR expression and binding affinity in the patients with Cushing’s syndrome was found. No correlation was observed between plasma cortisol concentration or 24 h urinary free cortisol and GR expression or binding affinity in Cushing’s syndrome patients. Conclusion The expression level and binding affinity of GR are obviously decreased in Cushing’s syndrome patients, which suggests 1.6 times of physiological dose of glucocorticoid for the patients with hypocortisolism after surgery, in order to overcome glucocorticoid resistance and maintain physiological function of glucocorticoid.