Abstract: In order to quantitatively evaluate the degree of pollution of heavy metals in the downstream soil by a gold mine, based on the potential ecological hazard index method and the risk evaluation coding method, the ecological risk of the soil is evaluated from the two dimensions of total amount of heavy metals and chemical morphology, and on the basis of analyzing the correlation between the enrichment coefficient of heavy metals and the sub-ecology and the original ecology, the Pb isotope ratio is applied to trace the source of heavy metals in the soil. The results showed that with the increase of the distance from the mine, the heavy metals in the soil except Cr gradually weakened. Soil heavy metals are generally at low risk. Cd has a high single coefficient (mean value of 72.50), but its active state proportion is relatively low, concentrated in 10% to 17%, while Pb, the total amount is small, but has a higher proportion of active state, concentrated in 15% to 30%, Pb, Cd elements brought by the potential ecological risks should be paid attention to. There was a significant correlation between the sub-ecological content of Pb, Cd and Zn and their enrichment coefficients, and the R² values were 0.765 7, 0.911 5 and 0.602 9, respectively, indicating that these three heavy metals were more related to the production activities in the mining area, that is, anthropogenic sources were more likely, while Cu and Cr were mainly based on natural sources. The Pb isotope ratio relationship showed that the soil sample as a whole was located between the tailings source (anthropogenic source) and the soil-forming matrix (natural source) terminal element. With the decrease of the distance from the mine, the heavy metal content and exchangeable state showed a generally increasing trend, and the isotope ratio of ²⁰⁶Pb/²⁰⁷Pb showed a downward trend, which was more inclined to anthropogenic sources, indicating that the production activities of the mining area contributed more to the heavy metals imported in the soil area near the mining area.