This paper elucidated the characteristics of geographical epidemiology from the angle of disease ecology. Among them the apparent endemic distribution is the most important charaeteristics. It shows that the disease is closely related to natural environment. Obviously, there exists a KaschinBeck’s disease belt and two non-disease belts in China. According to the natural features of disease-areas, eight envromental groups of diseae-areas can be divided and respectively were merged into three types. The main feature of chemical geography in Kaschin-Beck’s disease area is just like that in Keshan disease area, selenium content in environment in the affected areas is always lower. Hence, the two diseases often emege simultaneously in many cases, but Sometimes in some areas, such as in the area with lower selenium content, one of ths two occurs alone. In this paper, the authors made an approach to disese-cause of Kaschin-Beck’s disease. The low selenium content in environment is a basic factor in appearence of Kaschin-Beck’s disease, but some other factors must be taken into account. All of factors was called compound factors. The other factors include (1) Vitamins, for example Ve, (2) Some life elements related with selenium, such as Cd, Hg, Ag, Mo. Fe, Sr, Zn, etc.,(3)Some organic matter or some toxins in affected areas,(4) Some habits.