Abstract: To investigate the effects of nitrogen fertilization on litter decomposition and soil carbon mineralization, the litters and soil were collected in the Larix olgensis plantation which were fertilized for 3 years with different nitrogen fertilization（0 g/（m~2·a）（Control）; 5 g/（m~2·a）（low nitrogen）; 20 g/（m~2·a））（high nitrogen）. After being incubated for 140 days in laboratory, the rates of litter mass and organic carbon mineralization were measured. The results showed that, at the end of incubation, the loss rates of litter mass and litter organic carbon with different nitrogen fertilization were 33.0%-41.6% and 34.1%-42.9%, respectively. They both increased with the increase of nitrogen fertilization levels, and those in the high nitrogen treatment were significantly higher（P＜0.05） than those in the low nitrogen treatment and control. Compared with the control, the cumulative CO₂ effluxes of soil under low nitrogen and high nitrogen treatments decreased by 7.6% and 3.2% respectively, and the difference between low nitrogen treatment and control was significant（P＜0.05）. During the incubation, the concentrations of soil, available nitrogen（NH■-N+NO■-N）, soil microbial biomass carbon and nitrogen all increased with the increase of nitrogen fertilization levels. Correlation analysis showed that the loss rates of litter mass was significantly positively correlated with the concentrations of soil NO■-N and available nitrogen（P＜0.01）, while it was significantly negatively correlated with litter C/N（P＜0.05）. The cumulative CO₂ efflux of soil was significantly positively correlated with NH■-N concentration（P＜0.05）. By increasing soil nitrogen supply capacity, nitrogen fertilization could reduce litter C/N, which further accelerated litter decomposition and reduced soil organic carbon mineralization. Thus, nitrogen fertilization can increase soil organic carbon storage in Larix olgensis plantation.