Abstract: Abstract: To determine the geochemical background and anomaly is the key to geochemical prospecting. The influence of the lithologic characters on the background values of many elements, whether for stream sediment measurements or for soil geochemical measurements, is very conspicuous. It is unreasonable to delineate anomalies using the same lower limit of the anomaly in an area with complex geological conditions. The influence of the lithologic character on the background values of ore-forming elements is confirmed based on the relationship between oxide (SiO2) and ore-forming elements of geochemical samples. The lower limit of the anomaly of the ore-forming elements obviously affected by the lithologic character can be determined by the residual confidence belt using the linear regression model. The examples demonstrate that the method eliminates the influence of the lithologic character on the background values of many ore-forming elements to a large extent and distinguishes the background and anomaly of elements effectively.