Abstract: In Dachebeigou area of Jilin Province, the geochemical field varies significantly across different geological backgrounds. Consequently, using a unified anomaly threshold to delineate anomalies across the entire area in geochemical data processing yields poor mapping results. Based on the distribution characteristics of the geochemical field in the study area, integrated with the geological background, geological subareas were first divided. Subsequently, the anomaly thresholds of elements at sampling points within different subareas were used to calculate anomaly contrast values, and single-element anomalies were delineated accordingly. Taking Nb as an example, the anomalies delineated by this method not only solve the problem of undetected anomalies in low-background and low-field areas but also prevent the problem of excessively large anomalies in high-background and high-field areas. The results align well with the geological background and effectively reflect the known mineral occurrences. During the verification of key anomalies, new mineralization clues were discovered, confirming the effectiveness of the contrast value method in extracting anomaly information under complex geological backgrounds.