【Objective】 Understanding the characteristics and differentiation of soil iron oxide in subtropical karst basins is crucial for comprehending the occurrence, development, and type evolution of soil in this unique regional complex. 【Method】 This study focused on 53 typical soil profiles in the Houzhai River Basin, Puding County, Guizhou Province. The research involved measuring the content of various forms of iron oxides in diagnostic surface and subsurface horizons, calculating their weathering indexes, and analyzing the characteristics and differentiation of soil iron oxides. Additionally, the study explored the impacts of soil-forming environments and soil attributes on the characteristic differentiation of iron oxides.【Result】The results revealed an increasing trend in the content of total iron and free iron from diagnostic surface to subsurface horizons, with average increments of 25.54% and 39.63%, respectively. Iron oxides exhibited enrichment in diagnostic subsurface horizons. The activation degree of iron in the diagnostic surface layer surpassed that in subsurface horizons, while free iron and the iron crystal gel rate showed an opposite trend. Most tested diagnostic tables' subsoil had over 30 g·kg^-1 of free iron, over 50% iron dissociation degree, and less than 30% iron activation degree, indicating that the soil was in the aluminization stage during the middle phase of desilication. Factors such as parent rock, land use, watershed position, organic matter, pH, clay CEC₇, and texture types significantly influenced the iron oxide content and weathering index of various soil forms. Geographical detector analysis highlighted the significant explanatory power of parent rock and organic matter on iron oxide index differences (excluding free iron degree), with the highest Q value observed in their interaction (total iron 41.9%, free iron 39.8%, amorphous iron 40.1%, iron activity 41%, iron crystal gel ratio 52.5%).【Conclusion】Apparently, parent rock and organic matter are the primary factors influencing the differentiation of soil iron oxide characteristics in subtropical karst watersheds.