Abstract: Establishing safety threshold of heavy metal in soil is important to ensure quality safety of agricultural products in China. This study investigated the enrichment and transport characteristics of five heavy metals: Cr, Cd, Pb, As and Hg in different organs of maize and wheat in Jinchang City, Zhangye City, and Baiyin City under field conditions. The relationship between crop roots, stems, grains, and the total amount of soil Cr, Cd, Pb, As and Hg was established to determine the safety threshold in maize and wheat planting systems. The enrichment pattern of Cr, Cd, Pb, As and Hg in wheat different organs is consistent in the order of root>stem>grain. Similarly, the enrichment pattern of Cr, Pb, As and Hg in corn plants is in the order of root>stem>grain, while the enrichment pattern of Cd is in the order of stem>root>grain. The regression model between heavy metals in grain and the total amount of heavy metals in soil is established by regression analysis method. The prediction safety threshold of Cr, Cd, Pb, As, and Hg total amounts obtained through these regression model for corn is 434, 12.8, 378, 231, 9.74 mg·kg⁻¹ in soil, respectively. While corresponding total amount safety threshold for wheat is 119, 1.49, 115, 149, 15.8 mg·kg⁻¹, respectively. Through multiple factor stepwise regression analysis, it is found that soil pH, organic matter, soil calcium carbonate, and total heavy metal content are important factors affecting the Cr, Cd, Pb, As and Hg contents of corn grains. Logarithmic models could be used to fit, and the degree of fitting is significant. However, the above factors have no significant impact on the Cr, As contents in wheat grains. Using this equation can better predict the heavy metal content in calcareous soil corn and wheat grains.