Based on a long-term field experiment initiated in 1989 and conducted in the National Agro-Ecological Experiment Station located in Fengqiu County, Henan Province, China, dynamic changes of microbial biomass C and N, and microbial activity during the growth period of summer maize as related to different continuous fertilization management were investigated in 2007.At the same time, effect of long-term fertilization on microbial biomass and activity and their relationship with soil organic carbon content was also discussed. The experiment was designed to have 7 treatments, i.e. organic manure (OM), half organic manure plus half fertilizer N (1/2OM+1/2NPK), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (PK) and control (CK).Results show that temporal variation of soil microbial biomass C and N, and microbial activity was significant during the growth period of summer maize. The dynamics of microbial biomass C and microbial activity were consistent, and their extremely positive correlation suggests that microbial biomass C can be used as an indicator of microbial activity.Fertilization significantly affected soil microbial biomass and microbial activity.The 7 treatments generally showed a decreasing order of OM > 1/2OM+1/2NPK > NPK > NP > PK > NK > CK indicating that organic matter was beneficial to soil biochemical environment and soil microbial activity.Compared with Treatment OM, the other chemical treatments revealed a trend of decreasing soil microbial biomass and weakening microbial activity.It was particularly significant in treatments unbalanced in nutrient, with Treatment NK showing the worst effect, probably because element P is an important element for making up cell wall and membrane for most bacteria.Positive relationship of microbial biomass and enzyme activity with soil organic C was also observed.