【Objective】Soil organic nitrogen directly reflects the nitrogen supply capacity of soil. Therefore, it is important to clarify the mechanism of the effect of organic fertilizer on soil organic nitrogen components. 【Method】This study was based on the long-term positioning experiment started in 2008, and four fertilization treatments were set up (no fertilization CK, single application of organic fertilizer M, single application of chemical fertilizer NPK, and combined application of organic and inorganic fertilizer MNPK) to explore the effects of long-term different fertilization on the content of soil organic nitrogen components in apple orchards on the Weibei dryland. Besides, the key mechanism of increasing organic fertilizer to improve soil organic nitrogen content was studied through soil organic nitrogen component determination and metabolomics analysis of nitrogen metabolites. 【Result】The results showed that compared with NPK treatment, the contents of soil water, available phosphorus, available potassium, soluble organic nitrogen, and microbial biomass nitrogen in MNPK were increased by 4%, 33.8%, 41.7%, 8.2%, and 21.7%, respectively. Also, the content of acid hydrolyzed total nitrogen and acid ammonium nitrogen increased by 10.1% and 8.9%, respectively. The amino acid nitrogen content of M treatment was significantly higher than those of other treatments during the whole growth period, followed by MNPK, and CK was the lowest. Soil organic nitrogen components were significantly positively correlated with soil total nitrogen, microbial biomass nitrogen, and available nutrients (available phosphorus and available potassium). Except for non-acid hydrolyzable nitrogen, each organic nitrogen component was significantly positively correlated with acid-hydrolyzed total nitrogen. Metabolome results showed that the nitrogenous organic compounds in MNPK treatment were significantly higher than those in other treatments, and the proportion of amino acid nitrogen in the application of organic fertilizer treatment was higher than those in other treatments. Compared with NPK and CK treatments, amino acids accounted for an important proportion of nitrogenous organic compounds upregulated by MNPK treatment, and 8 amino acids were included in 45 nitrogenous organic compounds. The relative abundance was significantly positively correlated with available phosphorus, available potassium and soluble organic nitrogen. 【Conclusion】 The results showed that the improvement of soil physicochemical properties with increased application of organic fertilizer was conducive to organic nitrogen decomposition and turnover of amino acid nitrogen.