Abstract: When studying the biologic adaptability by using biologic vital element-manganese in the laboratory, G.Bertrand found that plant can't live if there is the lack of a certain vital element and that if the element is sufficient enough, the plant may live very well, but it may be poisoned or even die if the element is so much. While E.D.Weinberg expanded the G.Bertrand law and further revealed that certain quantity of manganese may allow some bacteria to grow well but may not be suitable for them to produce bacteriophage. Biologic vital double threshold element content and its physiological effect can be expanded to different hydrogeochemistry zones in hydrogeologic unit. In elements lioxiviated (leached), transferred strongly hydrogeochemistry zone, biologic physiological effect and element content show negative correlativity. In elements enrichment, lioxiviated, concentration by evaporation hydrogeochemistry zone and environment polluted by some elements superfluous, biologic physiological negative effect and element content show positive correlativity, between them which above is the element content fitting zone. Take the Lishi-Liulin hydrogeologic unit of Shanxi Province as an instance: The lack of selenium, iodine and fluorine in the hydrochemistry zone with element leaching and loss causes KBD, IDD, and tooth decay, which is in a negative correlativity with element content, respectively. While in the element lioxiviation and enrichment zone, fluorine is superfluous. As a result, endemic fluorosis occurs and its sick rate shows positive correlativity with content.