Objective: To investigate the relationship of serum 25-(OH)D expression with BMI and waist circumference in obese patients. Methods: A total of 120 obese patients were selected and included in the obesity group, and 100 non-obese patients were included in the control group during the same period. The level of 25-(OH)D was detected by automatic chemiluminescence immunoassay. The obese patients were divided into normal, decreased and deficient subgroups according to the expression of 25-(OH)D. Correlation anal. of serum 25-(OH)D expression was performed by Pearson test. The regression anal. was carried out using multiple linear regression equation and logistic regression model. Results: The incidence of 25(OH)D deficiency in the obese group was significantly higher than that in the non-obese group (P < 0.05). Leptin, neuropeptide Y, IGF-1, BMI and waist circumference in the 25-(OH)D deficient group were significantly higher than those in decreased group, normal group and non-obese group (P < 0.05). The expression of 25-(OH)D serum was significantly neg. correlated with leptin, neuropeptide Y, ICF-1, BMI and waist circumference (P < 0.05). Leptin, neuropeptide Y, ICF-1, BMI and waist circumference were independent risk factors for the expression of 25(OH)D (P < 0.05). Multivariate Logistic regression anal. showed that 25-(OH)D, LDL-C, HDL-C, leptin, neuropeptide Y and ICF-1 were independent risk factors (P < 0.05). Conclusion: The down-regulated expression of 25-(OH)D is closely related to the increase of BMI and waist circumference, which can be used as an important indicator to evaluate and predict the occurrence of obesity.