Soil and crop samples were collected from the major cropland in Yangzhong Area of Jiangsu Province for assessment of soil environmental quality with the single pollutant index method and the Nemerow comprehensive index method, according to the national standards for environmental quality of farmland producing hazard-free agricultural products and the soil indices for eight heavy metal pollutants. Results indicated that the soils were slightly polluted. Of the eight heavy metals, Cd and Hg pollution in the soil may be related to high-rated application of chemical fertilizer and pesticide; As, Pb, Cu and Zn pollution to exhaust gases from factories and automobiles; while Cr and Ni pollution mainly to the calcareous parent material in the Changjiang River valley. With the data in 1990 as basis, calculation was conducted for accumulation rates of these heavy metals, reflecting continuous heavy metal input. The study on eco-effect of heavy metals on agricultural products in the polluted region revealed that heavy metal pollution has turned out to be a threat to safety of the agricultural products.