Abstract：Micro-humic acid in drinking water can form stable complexes with heavy metals in the water, which might affect the modes of occurrence, movements and transformations of heavy metals. It is thus important to measure the content of humic acid in the water for assessing the relationship between the geological environment and the endemic disease. There exist quite a few measurement techniques for humic acid in the laboratory, but most of them are not suitable for rapid detection in the field. On the basis of analyzing characteristics of every detecting means, the authors put forward the colorimetry for detecting the humic acid in the water. Ports-15 spectrometer with 1cm optical fiber color comparison probe and 650nm wavelength red light was used in the laboratory for the test,. As a result, the curve for the relationship between the thickness of the humic acid and the absorbency was drawn.