Abstract: The determination of thresholds of chemical elements is one of the important problems in geochemical exploration. At present, there is not a scientific way to confirm the thresholds.The traditional way to determine the thresholds of chemical elements is based on the assumption of normal distribution of the element contents or their logarithms. In fact,the space distribution of geochemical element content is extremely complex; and the studies showed that the geochemical landscape may be a lowdimensional chaotic attractor system. The background values and anomalies of the elements have their own exponential relationship, which lead to a multifractal distribution, thus obtaining the anomaly threshold of element through the distribution of fractal elements. In this paper, the method of dividing area of geochemical exploration sample analysis data in Yangmingshan in Hunan is adopted. The threshold is determined through mixed application of fractal and traditional methods according to the distribution of data，drawing out the Sn anomaly map. It obtained better performance than by using the traditional method only, and the abnormal area enclosed by the element anomaly thresholds which is determined by the new method highly conformed to the known ore spots.

Key words: element anomaly threshold, contentarea, MAPGIS, Yanmingshan area of Hunan Province