Effect of long-term fertilization and mulching on soil microbial biomass carbon and nitrogen was studied according to the data of a long-term brown earth located experiment.Long-term fertilization and mulching increased soil microbial biomass carbon(BC) and microbial biomass nitrogen(BN).BC and BN of treatments applied manure,chemical fertilizer and manure combined were obviously higher than those of application of chemical fertilizer single or no fertilization.The results of correlation analysis showed that BC and BN significantly correlated to organic carbon and total nitrogen.BC and BN could be considered as an important indicator for soil fertility assessment.