By using ¹⁵N techniques, effects of urea and KNO₃ on processes of N₂O production in Hydragric pad dy soil and Gleyic paddy soil, collected from Wuxi and Yingtan, respectively, were invest igated under flooding condit ions at 25.In the Hydragric paddy soil, N₂ was a predominated product of denitrification process.Addition of KNO₃ stimulated DNRA process and hence N₂O product ion.In the Gleyic paddy soil, N₂O was produced from denitrification and aerobic denitrification processes with its product ion rate increasing with soil pH and nitrate concentration.It was observed in some treatments of both the soils that the ¹⁵N abundance of N₂O was larger than those of all the inorganic nitrogen, NH₄⁺, NO₃^-, and NO₂^-, implying that the processes for N₂O production would take place inside cells of microbes.