Yutangba, where a sudden incidence of human selenosis occurred in 1963, is located in the northern part of Shuanghe community about 81 km SE of Enshi City, Hubei Province, China. In Yutangba, native Se extensively exists within Se-rich carbonaceous rocks, abandoned stone coal spoils and high-Se soils close to Serich carbonaceous strata. The distribution of native Se is parallel with Se-rich carbonaceous strata, with local circles or strips. Selenium particles become sparse from the Permian Maokou to Wujiaping formation along the dip. Native Se is probably the main dominance, and once formed, will be re-deposited in special sites such as near water table. However, when Se-rich stone coal removed from deep as a fuel or fertilizer, a large amount of native Se will be quickly oxidized again and transformed to soluble Se, which will be enriched in local food via water irrigation systems. So, Se-rich carbonaceous strata are a necessary condition for the incidence of Selenosis, and human cultivating manner and activities such as mining stone coal as a fuel or fertilizer will provide a sufficient condition for oxidation of elemental Se and its transportation. When soluble Se is accumulated to a certain extent and is under the suitable environmental condition, selenosis would occur again in some places of Enshi Prefecture.