The microbial biomass C, N and the activities of enzymes, including catalase, invertase, urease and phosphatase, were investigated in five paddy soils with different utilized years, from 50 a to 2000 a, and the correlations between these biochemical properties in paddy soils and the utilized years were estimated. Both soil microbial biomass C and N tended to decrease with the increased utilized years, and the biomass N was more sensitive to reflect the difference caused by utilized years (p = 0.091). With increased utilized years, soil catalase activity decreased significantly (p = 0042) and invertase activity tended to decrease, while urease activity had nondirective alteration, but the phosphatase activity increased evidently (p = 0.022). The results suggested that, the sustained utilization of paddy soil could decrease the biomass and the total activity of soil microbial community, but could not result in the decline of soil fertility. Our result also indicated that, the sustained utilization had a potential to increase phosphorus supply capacity of paddy soils, but may not affect the nitrogen supply capacity.