Abstract: Heavy metal contents in top soils of Farming-grazing transitional zone and their differential characteristics were studied in the presented paper through field soil investigation.Averages of total Cu,Zn,Cd,As and Hg,except Pb and Cr,in the 102 selected soil samples were higher than the contents in top soils based on the second general survey of soil of Inner Mongolia province;besides,the result were also higher than the background values of the whole world.Particular,the contents of Hg was 3.3 times than the background values of the whole world and the index of Hg exceed the threshold levels according to the second grade of standards for soil environmental quality of China（GB15618-1995） was 8%.Moreover,the differential characteristics of the heavy metal contents were excessive in differential soil type.