Vitamin D insufficiency and deficiency is pandemic in the world.Sichuan Basin has a subtropical monsoon climate with China's lowest sunshine totals. Inferably, the prevalence of vitamin D insufficiency/deficiency in Sichuan basin is high, and possibly the highest in China. This study will research the serum 25OHD level to get the prevalence of vitamin D deficiency and insufficiency of urban and rural residents in Sichuan Province, China.