Abstract:Soil microorganism plays an important role in material cycling and energy transformation in 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 investigations and lab experiments were carried out to study characteristics of microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) in surface soil (0-20 cm). Three soil types（including latosolic red soil from Shaoguan, red soil from Guangzhou, and latosol from Leizhou） of Guangdong Province and four land use patterns （including grassland, forest, farmland and orchard ）were included in this study. Results showed that there were significant differences between MBC and MBN both respond to different land use patterns and different soil types and such differences were more significant for land use patterns. The MBC and MBN were much higher in the forestland and orchard than those in the farmland and grassland. Results further revealed that total organic carbon (TOC) and total nitrogen (TN) were also higher in the orchard than those in the other three land use pattern. However, compared to land use patterns, soil types had much less impacts on the MBC and MBN. Analysis of microbial quotient showed that land use patterns had different impacts on TOC and MBC.A correlation analysis showed that soil MBC, MBN, TN, TOC, and available N were all significant and positive correlated. The significantly and positively correlation between MBC and MBN suggested that The contents of MBC and MBN significantly correlated to those of SOC and TN，this suggested the contents of soil MBC and MBN were the sensitive indicators for characterizing of changes of soil fertility.