In southwest Shandong Province, high fluorosis in drinking water caused by high fluoride groundwater seriously affects the health and well-being of local people. Fluorine concentration in groundwater is a very complex hydrological and geochemical process. Water chemical test results indicate that fluoride content is 0.05~6.7 mg/L, 1.20 mg/L on average, and high-fluorine areas are mainly distributed in the juncture between the Jiaxiang Yellow River alluvial-pluvial plain and piedmont alluvial-pluvial plain as well as the interstream depression of the Yellow River alluvial- pluvial plain in Caoxian County, Shanxian County and Heze. Fluorite content of the groundwater has no distinct relationship with pH and mineralization intensity but is positively and negatively correlated with relative values of K++Na+ and Ca2+ respectively and obviously correlated with Ca2+ content. The authors probed into the hydrogeochemical genetic mechanism of the shallow-layer high-fluorine groundwater in the aspects of geological environment, hydrogeological environment and hydrogeochemistry, and studied the formation mechanism of the high-fluorine groundwater in the plain formerly flooded by the Yellow River. The results obtained by the authors are of important theoretical and practical significance for determining the cause of the fluorine-related endemic diseases, formulating the measures for prevention and cure of such diseases, and finding low fluorine groundwater suitable for dring.