Effects of conservation tillage on soil microbiomass,active soil microbiomass,respiration quotien,and enzyme activities were studied by field experiment.Results showed that straw returning could significantly increase soil microbial biomass and active microbiomass.Subsoiling with straw returning could siginificantly active microbiomass.The longer time after tilth,the smaller active soil microbiomass.Straw returning could increase soil respiration by 99.7% in the earlier stage(over-wintering stage) and reduce soil respiration by 16.6% in the later stage(seeding-sprouting stage).Compared with conventional tillage with no straw returning,conservation tillage could increase soil respiration in the earlier stage after tillage and reduce soil respiration in the later stage and reduce the loss of soil carbon,of which rotary tillage with straw returning was the best.Subsoiling returning could significantly increase soil urease activity and sucrase activity.Soil respiration and active microbiomass were good indexes of soil microbial characters and soil enzyme.