Abstract: The water quality of deep water in 1000square kilometers area and shallow water in 600 square kilometer area of western Huhehaote Basin was analyzed. The results show that both deep water and shallow water are rich inarsenic. Arsenic content in1.8%of shallow water and 40.9%of deep water is higer than the National Sanitary Standard fordrinking water of China. Arsenic in the water exists mainly inthe form of arsenious state. The contents of dissolved oxygen,sulphate,nitrite and selenium are all lower. Some water samples are high in fluoride.Iron ion and manganese ion are traceelements in the water. These phenomenons indicate that thereis the powerful reducing environment of rich organic substancein the area,in which arsenic is easily moved and accumulated.These are helpful in the occurrence of drinking water arsenicpoisoning case.

Key words: endemic arsenic poisoning, trace element, drinking water