In order to comprehensively evaluate the application effect of organic fertilizer instead of chemical fertilizer and guide the scientific fertilization of rice fields in southern China, the effects of partial substitution of chemical nitrogen with different proportions of organic nitrogen on soil organic nitrogen components were studied. The experimental site located in the scientific research and test base of Hunan Academy of Agricultural Sciences, Gaoqiao town, Changsha county, Hunan province. Five treatments were set up: single fertilizer treatment(NPK)，15% organic fertilizer replacement treatment(15M)，30% organic fertilizer replacement treatment(30M)，45% organic fertilizer replacement treatment(45M)，60% organic fertilizer replacement treatment(60M). After the late rice harvest in 2021, the contents of total nitrogen, soluble organic nitrogen, microbial biomass nitrogen and organic nitrogen components in 0-20 cm soil layer were determined. The results showed that the partial substitution of organic nitrogen for chemical nitrogen significantly increased the total nitrogen content in the topsoil of paddy field compared with NPK treatment. Under the condition of equal nitrogen and phosphorus input, the total nitrogen content in the soil treated with 15M, 30M, 45M and 60M were increased by 2.73%, 10.93%, 11.47% and 20.77%, respectively, compared NPK treatment. The contents of soil soluble organic nitrogen and microbial biomass nitrogen were increased by 24.53%-72.89%, and 0.92%-44.42%, respectively. Partial substitution of organic nitrogen for chemical nitrogen increased the contents of acidolytic amino acid nitrogen, acidolytic ammonium nitrogen and acidolytic amino sugar nitrogen, and decreased the contents of non-acidolytic nitrogen. Soil total nitrogen was significantly positively correlated with soluble organic nitrogen and microbial biomass nitrogen, and soluble organic nitrogen and microbial biomass nitrogen were significantly positively correlated with soil acidolytic ammonium nitrogen, acidolytic amino acid nitrogen and acidolytic amino sugar nitrogen. Compared with single fertilizer application, partial substitution of organic nitrogen for chemical nitrogen increased the contents of total nitrogen, active nitrogen(soluble organic nitrogen and microbial biomass nitrogen), acidolytic amino acid nitrogen, acidolytic ammonium nitrogen and acidolytic amino sugar nitrogen in soil, which was beneficial to improving the nitrogen supply capacity of soil. Soil acidolytic ammonium nitrogen, acidolytic amino acid nitrogen and acidolytic amino sugar nitrogen are the key factors affecting soil active nitrogen. In this study, 60% organic fertilizer replacement treatment has the best fertilization effect.