Semi-arid sandy lands in Northern China are crucial ecological barriers, yet large-scale patterns and controls on their soil C, N, and P stoichiometry remain poorly quantified. This study investigated vertical and regional patterns of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents and their stoichiometric ratios in the Horqin (HSL) and Hunshandake sandy lands (HDSL) to elucidate the controlling mechanisms. We analyzed SOC, TN, and TP in soil profiles (0-100 cm). Redundancy Analysis and Random Forest models quantified the effects of climate, soil properties, and vegetation factors on soil C, N, and P stoichiometry. HDSL soils had significantly higher SOC, TN, and TP contents than HSL. We identified a clear hierarchical control: nutrient contents were primarily determined by silt and clay content (SC), whereas their stoichiometric ratios were co-regulated by multiple factors. The C:N ratio was primarily influenced by mean annual temperature (MAT) and precipitation (MAP), while C:P and N:P ratios were controlled by SC, MAP, pH, and MAT. Notably, the weak correlation between TP and the C:P or N:P ratios indicates a decoupling between TP patterns and the tightly linked C and N dynamics. Our findings reveal a dichotomy of controls: soil texture dictates absolute nutri-ent stocks, while a complex interplay of texture, climate, and pH regulates their relative balance. This hierarchy drives a decoupling of the TP pool from the tightly linked carbon and nitrogen cycles, offering critical insights for predicting ecosystem responses to environmental change