Abstract: This paper analyzed the current situation of heavy metal contamination in  cropland soils in China, and discussed the input, output, and balance of heavy metals in  cropland ecosystems. It was considered that heavy metals had definite accumulation in cropland ecosystems, but overall speaking, this accumulation had relatively small environmental risk, and only some plants, especially vegetables, accumulated heavy metals over the standards. In mining areas, adjacent areas of smelting plants, and the farming areas using larger amounts of related wastes, the heavy metals content in plants and soils was at least ten times higher than that in normal croplands, existing larger environmental risk. Aiming at the current situation of heavy metal contamination of farmland soils in China, some effective regulation measures for the heavy metal cycling in the cropland ecosystems were proposed, and the further research prospects in related fields were discussed.

Key words: heavy metal, agro-ecosystem, cycling, regulation, freeze-thaw processes, terrestrial ecosystem, nitrogen cycle, process, mechanism.