This study was conducted to determine the contents of soil microbial biomass carbon(BC),and nitrogen(BN),K_2SO_4-extractable organic carbon(DOC),and nitrogen(SON) in three different soil types and under two different use patterns in the south part of Loess Plateau.The results showed that the contents of BC,BN,DOC and SON in the forest soils were higher than those in the arable soils;and the concentrations of these parameters in the forest litter were significantly higher than those in the 0~20 cm soil layers.Under the different agricultural cultivation,the concentrations of BC and BN in the anthrosols were higher than those in the isohumisols and the argosols.The concentration of DOC in the argosols was higher than that in the anthrosols and the isohumisols.The concentration of SON in the isohumisols was higher than that in the anthrosols and the argosols.Soil types had significant effect on the concentration of BN,but had no significant effect on the concentrations of BC,DOC and SON.The ratios of BC to soil organic C(BC/TC),and BN to soil total N(BN/TN) were significantlyhigher than the ratios of DOC to TC(DOC/TC),and SON to TN(SON/TN).There were significant positive correlations between BC,BN and DOC,SON,indicating the close relationships between BC,BN and DOC,SON.