Abstract: In order to find out the effect of nitrogen on the metalaxylM residue in the krasnozem, the nitrogen fertilizer levels of N0,N1/2,N and N3/2 were separately set for 00mg/kg,375mg/kg,750mg/kg and 1125 mg/kg and 81 mg/kg of metalaxylM were added in the incubation experiment and the pot experiment, and the metalaxylM residue were extracted by methanol, then were detected by gas chromatography with FID to research the degradation of metalaxylM in krasnozem under four different nitrogen levels. The results showed that metalaxylM residues were degraded with a process of adsorptiondesorption in soil, and the dissipation dynamics could be described by firstorder rate equation. The degradation speed rate of metalaxylM under nitrogen fertilizer levels of 750 mg/kg was the fastest among four different nitrogen fertilizer levels. The amount of soil microorganisms also rapidly reduced after the metalaxylM treatment during the 2h-7d, and returned at the 7th day. The microbe quantity in different nitrogen levels was N>N3/2>N1/2>N0;besides, it was significant among N,N3/2 level and others, but not significant between N and N3/2.Microbe quantity began to recover after 17 days. It suggested that both nitrogen and metalaxylM residue were energy substance for microorganisms, promoting their growth and propagation.