In the aim of understanding the characteristics of the microbial biomass in the farming soil derived from wetlands, detail field investigations were conducted in a selected landscape unit (112°16′～112°56′E，28°42′～29°11′N) in the Dongting Lake region of Hunan Province. Data suggest that paddy soils contained larger amounts of total organic C (TOC), total N (TN), and the microbial biomass C and N (BC and BN) than arable soils in this region. For paddy soils, the contents of TOC and TN were larger under double-rice cropping systems than under single rice cropping systems. However, the content of total P (TP) for soils was under slightly larger in arable soils but the content of microbial biomass P (BP) was slightly larger in paddy soils than in arable soils. It is surprising that, despite of the difference in the contents of TOC and TN resulted from double and single rice cropping systems, the content of BP maintained relatively consistent for all the paddy soils. BC, BN, and BP as the percentage of TOC, TN, and TP in the soils of this region varied from 0.65% to 7.24%(a mean of 3.00%)，0.98% to 7.41%(a mean of 3.81%)，and 0.16%-7.54% (a mean of 2.80%)，respectively. The ratio of BC to BN varied from 4.06 to 9.29(a mean of 7.26). The contents of BC and BN significantly correlated to those of SOC and TN (p<0.01), but not so between the contents of BP and TP. Significant correlations also existed the contents of BC, BN, and BP. This study suggests that land-uses and cropping systems resulted in significant differences in the contents of TOC and TN in soils in wetland regions, and that the contents of BC and BN can sensitively reflect changes in TOC and TN.