Abstract: Compared with ammonium bicarbonate(AB),the effect of modified ammonium bicarbonate (MAB) on nitrification and denitrification processes and NO and N₂O emissions in a clay soil (C soil) and a loam soil (L soil) was studied in laboratory (25℃ and 50% WFPS).The inhibition effect of DCD from MAB on nitrification was relatively small in C soil,but considerably great in L soil.Compared with AB,MAB extended 7 days and 33 days for retaining NH₄⁺.During 15 days,the NO emission from C soil and L soil respectively accounted for 0.60% and 1.06% of applied N under AB application (100μg N·g^-1 ),which were as 30 and 12 times as the N₂O emission from corresponding soils.After applying MAB,the emission of NO from C soil and L soil decreased by 67% and 95%,and the emission of N₂O decreased by 64% and 95%,respectively.After 39 days of aerobic incubation,then anaerobically flooded incubation with nitrate addition (200μg KNO₃-N·g^-1 ) for 7 days,the total loss of denitrification in MAB in L soil was 50% less,and N₂O emission was 113% more than in AB in same soil.