Abstract: Winter crops were essential for improving soil productivity and soil microbial biomass on paddy soils. The purposes of this study were to investigate the effects of winter crops on soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN) on a paddy soil in the south of China. Five treatments, namely annual ryegrass, Chinese milk vetch, rape, spring potato and winter fallow, were set up. The result showed that, winter crops significantly increased SMBC, SMBN and soil microbial quotients (MQ) compared to winter fallow（P0.05）. Before the harvest of winter crops, the SMBC in soil with annual ryegrass treatment (398.5 mg/kg) was significantly higher than the other treatments. The highest SMBN (97.8 mg/kg) was found in the treatment of Chinese milk vetch. During early stages of rice growth, winter ryegrass treatment significantly increased SMBC, but not the late stages. In conclusion, winter crops could improve soil ecology environment and soil microbial diversity.