Abstract: To clarify the change patterns of physicochemical properties and element ecological stoichiometry of soil profiles, and thus provide a scientific basis for understanding soil formation mechanisms and protecting soil resources, this study collected soil samples from Ustic and Udic Isohumosols in Heilongjiang Province of China based on the genetic horizons, and their physicochemical properties and element ecological stoichiometry were comparatively examined. The results showed that from A-horizon to C-horizon, the soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH₄⁺-N), available phosphorus (AP) and sand contents, as well as the surface mean diameter (SMD) and volume mean diameter (VMD) of soil particles decrease gradually; while the soil pH, clay and silt contents increase significantly. Notably, greater soil heterogeneities are observed in C-horizons (parent material horizons) than in Ah-horizons (humus horizons), and the variations of the physicochemical properties along soil profiles are greater in Udic Isohumosols compared to Ustic Isohumosols. In addition, the element ecological stoichiometric analysis found that soil C∶N, C∶P and N∶P decrease significantly with increasing soil depth in both Ustic and Udic Isohumosols, suggesting that the nutrient cycling processes in deeper soil horizons are more strongly constrained by carbon and nitrogen.