Soil microbial biomass and some enzyme activities in Hapli-Stagnic Anthrosols under different fertilization treatments were investigated by the incubation experiments in the laboratory.Soil microbial biomass C and N under chemical fertilizer application increased during the incubation period,while soil microbial biomass C increased in the early period of the incubation and then remained stable or decreased,and soil microbial biomass N increased generally under the treatments of chemical fertilizer mixed with organic manure.Soil urease activity under different treatments increased in the early period of the incubation and decreased lately,and acid phosphatase and invertase activities increased under chemical fertilizer application and decreased under the treatments of chemical fertilizer mixed with organic manure during the incubation.Compared with the CK (without fertilizer application),the chemical fertilizer application reduced significantly the soil microbial biomass and soil urease activity,especially under high amount of chemical fertilizer application,but influenced insignificantly acid phosphatase and invertase.Straw application increased significantly soil microbial biomass and enzyme activities,especially under high amount of straw application.However,the influence of pig manure on soil microbial biomass and enzyme activities was still uncertain because of high nutrient input with its application.It suggested that high amount of chemical fertilizer applied continuously is not favourable for the highly-intensified agriculture to maintain and increase soil biological quality,but straw directly-returned to soil may be an effective measure to maintain soil healthy state