Abstract: The Dexing copper mine is a superlarge porphyry copper deposit in Jiangxi Province. With the increasing mining activities, the environmental problem of heavy metals pollution have become more and more serious in the Dexing copper ore district. In order to improve the quality of the soil environment of the Dawu River in the Dexing copper ore district, the accumulation effect of heavy metal elements and the reasons should be understood. The authors selected three sections in upstream, midstream and downstream areas of the Dawu River, collected 50 samples, calculated the accumulation rate of heavy metal elements based on geochemical baseline and, on such a basis, revealed the accumulation characteristics. Generally speaking, the accumulation of Cu and Mo is important and clear, and the cumulative effect of Cr and As is obvious on the first- and second-order terraces of Dawu river basin, where the accumulation effect of heavy metals is remarkable. The authors also analyzed the factors responsible for the accumulation of heavy metals in the aspects of mineral association, geological setting, river terraces, topography, elemental speciation and mining process.