Soil, as a natural resource essential to human survival, can provide people with food and fiber they need in their daily life and production. In recent years of rapid economic development, people over-exploit the land and apply irrationally fertilizers, thus triggering a series of problems, like land degradation, reduced grain output, food security and so on, which in turn threatens sustainable development of the human society. Therefore, soil amelioration has become a problem attracting extensive concerns and discussions the world over. Corn stalk is a renewable kind of resource, rich in supply and ready for direct use. Northeast China is a major corn producing region of the country and turns out every year large volumes of corn stalk, which unfortunately is either used as cooking fuel or just burnt in the field, thus leading to a great waste of organic resource and pollution of the environment as well. In the case that the soil urgently needs fertilizing and mechanical farming improving, the practice of deep application of corn stalk is recommended to be an important measure to improve soil fertility, increase soil organic matter, and hence to promote agricultural production and guarantee people’s life. Soil organic matter is a key factor of fertile farmland and humic substances are important components of organic matter and considered to be the most abundant organic ingredients of the nature, and they play a critical role in the ecosystem. Humic substances can be classified, according to their solubility, into humic acid (HA), fulvic acid (FA) and humin (Hu). HA is a kind of polymer compound, complex in structure and soluble in base solution, but not in water or acid. HA is also an important extract of humus. From a field of Cinnamon soil fertilized for 3 years in a field experiment base in Xokoumo Village, Fuxin Mongolia Autonomous County, Liaoning Province, soil samples were collected in October 2012. The field experiment was designed to have two treatments, CK (no stalk applied) and CS (stalk applied at a rate of 24 000kg hm^-2). Each treatment had three randomly-selected sampling points, from which soil samples were gathered at 0~20 cm and 20~40 cm for analysis in lab. Water-soluble substances (WSS), humic acid (HA), fulvic acid (FA) and humin (Hu) were extracted using the modified humus component extraction method to explore effects of deep applied corn stalk on content of organic carbon in various humus components in the soil. Solid HA was extracted from the soil as samples for characterization of its structure through elemental composition analysis, differential thermal analysis and infrared spectral analysis. Results show that deep-applied corn stalk helped increase the content of organic carbon in the surface soil and in WSS, HA, FA and Hu therein, by 33.13%, 28.57%, 11.33%, 9.57% and 18.58%, respectively. It raised, somewhat, the content of organic carbon in WSS too, but reduced the content in HA and Hu in the subsurface soil; it lowered the relative contents of WSS, FA and HA in the surface soil to a varying extent, but did not vary much. The relative contents of all of them except WSS in the subsurface soil, to a varying degree; PQ values of the surface and subsurface soils did not vary much; From the perspective of element composition analysis, it is generally held that H/C and O/C are the factors characterizing condensation and oxidation levels of HA. Compared with CK, Treatment CS was relatively lower in H/C of HA in the surface and subsurface soil, indicating that deep-applied corn stalk raises the condensation degree of HA and complicates its molecular structure, and Treatment CS was higher in O/C of HA in the surface soil but lower in the subsurface soil, indicating that the application of corn stalk intensifies HA oxidation in surface soil, but lessens the reaction in the subsurface soil; The differential thermal analysis shows that the high/medium temperature values in exotherm and weight loss of HA in the surface and subsurface soils both went up, indicating that HA increases its aromatic structure and improves its thermal stability relatively; The infrared spectrum analysis shows that deep-applied corn stalk intensified C = O stretching vibration of HA carboxyl, C = C stretching vibration of aroma and C - O stretching vibration of aromatic ester, and moreover, the semi-quantity system analysis reveals that the 2920/1620 value was higher in CS than in CK, indicating that newly formed HA has strong aliphatic nature.