Abstract: In order to understand the dynamics of soil chemical characteristics (soil available phosphorus, soil available potassium and soil microbial biomass carbon, nitrogen) two types of tillage and different microbial inoculants during winter wheat growing periods based on straws returned in a field using the plots experiment. The results showed that two types of tillage had no significant effects on soil available phosphorus, available potassium, soil microbial biomass carbon and nitrogen content, but different growing stages showed the significant impact on these indices. Application of biogas slurry plant growth-promoting rhizo-bacteria or EM influenced the level of soil available phosphorus or soil available potassium in the rotary tillage markedly; Moreover, treatment of biogas slurry plant growth-promoting rhizo-bacteria or biogas slurry produced the effect on soil available phosphorus or soil available potassium in the deep tillage.The addition of plant growth-promoting rhizo-bacteria compared with control could reduce soil carbon nitrogen ratio, and enhanced the decomposition of straw. The soil available potassium in the root zone increased by 44.31% (rotary tillage) and 32.61% (deep tillage) comparing to that in the non root zone at the wheat harvest stage. Soil microbial biomass carbon or nitrogen in root zone was higher than that in non root zone for two types of tillage, and application of EM Strain improved the levels of soil microbial biomass carbon, microbial biomass nitrogen.