The objective of this experiment was to improve our understanding of soil organic N mineralization in the Loess Plateau. Typical soils were sampled from north to south in the Loess Plateau and soil organic N mineralization was measured in the soils using the Bremner incubation method. The soils were incubated for 60 d. The results showed that part of NH+4-N released during mineralization was fixed by clay minerals in these soils, so in order to get reliable results, we must consider this when determining total organic N mineralization. The amount of organic N mineralization was significantly different among the soil types. Specifically, the amount of mineralization decreased in the order Eum-Orthic Anthrosols > Los-Orthic Entisols > Hap-Ustic Isohumisols > Ust-Sandiic Entisols. The amount of organic N mineralization decreased from south to north across the Loess Plateau. The addition of Medicago sativa residue, which has a low C∶N ratio (C/N=21.7), increased the amount of organic N mineralization. In contrast, the addition of Stipa bungeana residue, which has a high C∶N ratio (C/N=43.3), increased microbial immobilization of soil mineral N. There were significant differences in the amount of organic N mineralization at 20d (p=0.0117), 40d (p=0.0109), and 60d (p=0.0073) depending on the type of vegetation growing on the soil at the time the samples were collected. The amount of organic N mineralization tended to decrease in the order: forest soil > bare land soil > grassland soil > farmland soil. The addition of (NH4)2SO4 to the soil resulted in a decrease in the N mineralization rate at 20d (p=0.0037), 40d (p=0.0033), and 60d (p=0.0027) compared to soils which did not receive (NH4)2SO4. There was a significant difference in the N mineralization rate among the different soil types when incubated for 20d (p=0.0092) and 40d (p=0.0381), however, there was no significant difference in mineralization rates among the soils(when incubated for 60d. Organic N mineralization rates tended to decrease in the order: Ust-Sandiic Entisols > Los-Orthic Entisols > Eum-Orthic Anthrosols > Hap-Ustic Isohumisols. The results showed that total organic N mineralization rates increased from south to north in the Loess Plateau.