The Loess Plateau is characterized by highly erodible soils, steep slopes and low vegetation coverage due to excess exploitation of land resource and improper land use, and the characteristics of soil nitrogen and its components have been the concern in the recent years. In order to clarify the distribution characteristics of typical soil total nitrogen, soil organic nitrogen and the correlation among the components of soil organic nitrogen from north to south on the Loess Plateau, based on different soil types and land-use patterns, the layers of 0–10 cm, 10–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, 80–100 cm, 100– 120 cm, 120–140 cm, 140–160 cm, 160–180 cm and 180–200 cm of typical soils of Ust-Sandiic Entisols (Shenmu), Los-Orthic- Entisol (Yan’an) and Eum-Orthic Anthrosol (Yangling) were collected and the contents of soil organic nitrogen and the correlations among soil total nitrogen, soil organic nitrogen, microbial biomass nitrogen, soil fixed ammonium, amino acid nitrogen, ammonia nitrogen and amino sugar nitrogen were analyzed. The results showed that the contents of soil total nitrogen and soil organic nitrogen were different under different soil types and soil depths. In the same location, the contents of soil total nitrogen and organic nitrogen in the profiles decreased remarkably within 0–40 cm, decreased slightly within 40–80 cm and remained low and stable under 80 cm soil depth．From south to north, the contents of soil total nitrogen and organic nitrogen decreased significantly. There were highly significant correlations (P<0.01) among soil total nitrogen, soil organic nitrogen and its components, microbial biomass nitrogen and soil fixed ammonium. Soil microbial biomass nitrogen had significant (P<0.05) or extremely significant (P<0.01) linear correlations with the contents of soil total nitrogen, soil organic nitrogen and most of components of soil nitrogen, but no linear correlation with amino sugar nitrogen and fixed ammonium nitrogen contents. Amino acid nitrogen was the important contributor to soil microbial biomass nitrogen.