Abstract: In a wheat-corn cropping system, the crop residues were crushed and incorporated into soil after harvest. The soil respiration and soil microbial biomass were compared one year later with soil that had doubled amount of residues incorporation or had no incorporated residues. The soil respiration was increased by the residue incorporation and the effect was more apparent when the incorporated residue amount was doubled. The soil microbial biomass was also increased by the residue incorporation. But the effect of the incorporated residue quantity was not significant. Seasonally, the maximum soil respiration appeared earlier than the maximum microbial biomass, but soon turned to decrease. The microbial biomass maintained the high level for a longer period, indicating there was maintenance respiration and biosynthetic respiration as well. The residue incorporation was suggested as a measure to increase the soil fertility, but doubling the amount of residue incorporation seems not necessary.