Abstract: Dali county is the high incidence area of fluorin illness,m ainly because of drinking ground water with high concentration of fluor in in along time.The content range of fluor in in ground water is 0.01-11.8mg/L based on the analysis of ground water samples in Dali county.The distributing character of fluor in in ground water is higher at north than that atsouth.The most fluorin-enriched areas are distributed in east of second and third terraces in Weiriver,with the high-fluorin area accounting for 63% of the total area.The main factors for enrichment of fluorin are the abundant sources of fluorin,the specific landform and physiognomy,the dry climate,and the slowex changing process of ground water.