Abstract: Chromium slag leachate is typically enriched in Cr(Ⅵ), a highly toxic and mobile species that poses significant risks to ecological environment. However, chromium behavior in multi-aquifer–aquitard systems remains insufficiently understood, particularly with respect to the key controls on its migration and transformation. In this study, a representative chromium-contaminated site was investigated to elucidate the migration and transformation patterns of chromium in soil under such conditions. The spatial distribution of Cr in soil at different depths, the different forms and proportions of Cr in uncontaminated and contaminated soils, and the factors such as iron and aluminum content in soil affecting the migration and transformation of Cr were analyzed by sampling and testing soil samples, and the combination methods of mathematical statistics, Kriging interpolation, and factor analysis. The results shown that (1) soil below ground surface 40 m was polluted by Cr with different degrees around the chromium slag heap, and the percentage of Cr(Ⅵ) mass fraction was higher in clay or silt clay than in sand layer. (2) The proportion of Cr in weak acidic state in soil at different depths was less than 10%, and the proportion of Cr in residual state ranged from 37% to 63% in uncontaminated soil; however, it mainly existed in the form of reducible state in contaminated soil. The weak acid-exchangeable and reducible states of Cr were the main forms of Cr migration and transformation at this site. (3) There was a linear relationship between the Fe and Al contents in soil at different depths, and the increases of Fe and Al could enhance the adsorption capacity of soil for Cr(Ⅵ), especially in the silty clay and clay layers. Increasing cation exchange capacity CEC promoted the adsorption of Cr(III) in soil at different depths. Manganese oxides favored the conversion of Cr(III) to Cr(Ⅵ) through adsorption, oxidation reaction, and microbial behavior, while organic matter drove the conversion of Cr(Ⅵ) to Cr(III). Soil pH exerts a fundamental control on chromium speciation and sorption behavior by regulating surface charge conditions and interacting with CEC and organic matter. Therefore, accurate identification of site hydrogeological conditions is essential for analyzing the transformations of Cr in soil. This study can provide strong support for risk management and post remediation of chromium slag contaminated sites.