Abstract: Comparing the similarity of virtual geochemical maps made from the data of different labs is a new method for geochemical analytical quality control and evaluation. But the comparison by eyesight could get only qualitative and fuzzy conclusions. By calculating the overlap areas of the maps and introducing the FFP evaluation principle, the similarity indexes of the maps would be obtained. Based on the similarity indexes, the similarity of the maps could be evaluated quantitatively. This method can be also applied to the research on element distribution and temporal and spatial variation of environmental pollution regions.