An experiment using the ¹⁵N -labeling method was carried out to investigate effects of application of ammonium nitrate (NH₄NO₃, N 300mg kg^-1) and nitrite(Na NO₂, N 1mg kg^-) on generation of N₂O and NO in mid- subtropical forest soils, different in water regime (60% and 90% of WHC), in Southeast China. Results show that in soils 60% of WHC in soil water content, generation of N₂O and NO was significantly inhibited by high nitrogen input (p <0.01 ) ; while in soils 90 % WHC in soil water content, a similar phenomenon was observed with the generation of N₂Owithin the first 9 hours of incubation, but afterwards the trend turned reversely; When NO₂^- added the inhibitions of high nitrogen input were lifted for all unsterilized soils, addition of NO₂^- immediately offset the inhibitive effect of high soil N content and triggered off generation of a large amount of N₂O and NO, forming a sharp contrast to CK (p <0.01 ). Such a phenomenon did not last long (for 21 h only) in soils 60% of WHC; but it did quite a long time (over 2 weeks) in soils 90% of WHC, which suggests that high water availability and exogenous NO₂^- played an important role in offsetting the inhibitive effect of high soil N content. In this experiment, N₂O was generated mainly in denitrification process of the soil, and what is more, the addition of unlabeled NO₂^-led to rapid increase of hybrid N₂O (¹⁴N¹⁵NO) molecules within the first 21 hours of the experiment, demonstrating that denitrification in the forest soil may probably proceed mainly through codenitrification by fungi, which may explain over 80% of the denitrification. Spearman rank correlation analysis indicates that there is a significantly positive correlation between the NO and N₂Oproduction rates (p <0.05 ) in non-sterilized soils, and the lower the soil water content, the higher the correlation between the two. After addition of NO₂^-, sterilized soil produced more NO than unsterilized soil, but almost no N₂O, which indicates that in acid soils chemical denitrification contributes more to NO than to N₂O.