Abstract: Soil microorganism plays an important role in material cycling and energy transformation of an ecosystem.Due to its sensitivity to environmental changes,soil microorganism is considered to be one of the key indicators to reflect the variation of soil quality.In this paper,field investigation and lab experiment analysis were carried out to study microbial biomass carbon(MBC) in surface soil(0—10 cm) in Huantai County,Shandong Province.Three soil types(Fluvo-aquic soil,Cinnamon soil and Sajiang black soil) and agricultural land use patterns(forest,vegetable and crop lands) were included in this study.Results showed that there were significant difference between MBC responded to different land use patterns,which increased in the order of crop land(440—480 mg/kg)> vegetable land(320—380 mg/kg) > forest land(240—330 mg/kg).MBC contents varied between different soil types,however,compared to agricultural land use pattern,the impact of soil type on the MBC was much less pronounced.For any type of soil,the content of N,P and K of vegetable land was higher than those of forest and crop lands;organic matter content of crop land was the highest,followed by vegetable and forest lands;and soil pH of vegetable land was lowest,followed by crop and forest lands.In addition,MBC had a significant positive correlation with total nitrogen(TN) and organic matter(P<0.01).There was a significant but weakly negative correlation between MBC and available phosphorus(AP)(P<0.05);whereas,there was no correlation between MBC and available potassium(AK) and pH.The correlativity between soil nutrients and MBC under different land use patterns was not consistent.Returning straw to field and applying organic fertilizer had a favorable effect on the soil MBC.