Nitrogen fertilizer significantly influences crop biomass, which will affect the amount of organic carbon into soil and soil carbon stability and accumulation. Based on located experiments, combining with two kinds of acid hydrolysis, this study analyzed the changes of soil acid hydrolysis carbon and residual carbon from acid hydrolysis under different nitrogen levels in black soil, to re⁃ veal the effects of different nitrogen treatments on chemical stability of meadow soil organic carbon. Five treatments were designed, including no application of N fertilizer(N0), 70% optimized appli⁃cation of N fertilizer(N168), optimized application of N fertilizer(N240), traditional high⁃amount application of N fertilizer(N270) and 130% optimized application of N fertilizer(N312). The re⁃sults showed that the changing trends of the organic carbon components obtained with the two hydrol⁃ysis methods were mainly consistent. Nitrogen fertilizer on the whole contributed to accumulation of total organic carbon in soil. Application of N fertilizer increased the content of organic carbon, the content of organic carbon under the four treatments was higher than N0(P0.05).Application of N fertilizer decreased the content of soil recalcitrance organic carbon, and N240 was significantly higher than other treatments(P<0.05). Indexes of organic carbon activity of N240 were similar to those of NO, but lower than other treatments. Recalcitrance index(RIC) rose significantly in N270 but lower in N240 and N0(P<0.05). Labile index(LIC ) of organic carbon significantly(P<0.05) increased in N270, but fell significantly in N312. Obviously the contribution of N fertilizer application is to increase the content of soil organic carbon by increasing the content of active organic carbon. Reasonable amount of N fertilizer can increase recalcitrance index(RIC) and improve the chemical stability of organic carbon. Therefore, content and stability of meadow soil organic carbon can be manipulated by optimizing N fertilizer application.%氮肥的施用会影响作物生物量，从而影响进入土壤中的有机碳的量，影响土壤有机碳的稳定性和积累。该研究在定位试验的基础上，结合2种酸解法，分析了不同施氮水平下黑土中土壤酸水解碳和酸解残留碳的变化，以揭示不同氮肥处理对草甸黑土有机碳化学稳定性的影响。试验设置5个处理，包括不施氮肥（N0）、优化施氮70％（N168）、优化施氮（N240）、传统高量施氮（N270）、优化施氮130％（N312）。结果表明：2种酸解法获得的有机碳组分结果变化趋势基本一致。施用氮肥增加了土壤有机碳含量，4个施氮处理有机碳含量显著高于N0（ P＜0�05），N240处理有机碳含量最高；施用氮肥提高了土壤中易酸解有机碳的含量，不同施肥处理中N240处理含量最低，N312处理含量最高，但施氮处理间差异不显著（ P＞0�05）；施用氮肥降低了土壤难降解有机碳的含量，N240处理显著高于其他处理（ P＜0�05），N240处理土壤有机碳活性指数与N0的相近，低于其他氮肥处理，N270显著提高了土壤有机碳活性指数（ P＜0�05），而N312显著降低了土壤难降解有机碳指数（ P＜0�05）。施用氮肥通过增加土壤活性有机碳含量来增加土壤有机碳的含量，合理的氮肥用量可以增加土壤中难降解有机碳指数，提高有机碳的化学稳定性。可以通过合理施用氮肥来调控草甸黑土有机碳含量及其稳定性。
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