Vitamin D is an essential lipid-soluble vitamin in human body, which is extensively involved in the development and differentiation, as well as growth and regulation of numerous human organs and tissues. Vitamin D is subject to multiple factors, including parathyroid hormone (PTH), calcium, intestinal absorbency, hepatic and renal function, skin, and muscle. Large scale epidemiological data suggest that, vitamin D insufficiency is prevalent worldwide. Prevalence of obesity tends to increase on a global scale. Vitamin D insufficiency is correlated with obesity, and the serum vitamin D level in obese population is markedly lower than that in normal weight population. Therefore, vitamin D intervention treatment among the obese population contributes to improving the body mass index (BMI). In this paper, the worldwide epidemiological features of vitamin D and obesity were summarized. Vitamin D and obesity interact mutually through environmental factors, personal factors and changes in molecular levels, so obesity causes insufficiency or deficiency of vitamin D.