In order to evaluate impact of planting Eucalyptus on soil fertility and eco-environment in the red soil region of China, soil samples were collected from Eucalyptus and Pinus massoniana plantations and natural broadleaf forests in Luzhai County, Guangxi (China) for analysis and comparison of biological properties and structures of bacterial communities in the soils under different forests, using PCR-DGGE and dilution plate method. Results show that the number of culturable microorganism, such as bacteria, fungi and actinomycetes in the Euclyptus forest soil was lower than in the natural broadleaf forest, but not much different from that in the Pinus massoniana forest soil. Pinus massoniana is an indigenous tree species of Guangxi. In addition，in terms of activities of soil enzymes that are involved in C, N and P recycling (β–Glucosidase, phosphatase and protease) the Eucalyptus plantation was inferior to the other two, and in terms of biomass C and N that characterizes soil fertility, it was inferior to the natural broadleaf forest, but did not have much regular difference from the Pinus massonianaplantation. Meanwhile, in terms of bacterial diversity index, richness and evenness, the Eucalyptus plantation was inferior to the natural broadleaf forest, but not much different from the Pinus massoniana plantation. All the findings indicate thatEucalyptusplantation, even though not so good as natural broadleaf forest, is more or less the same as Pinus massoniana in their impacts on soil fertility and ecological quality in degraded red soil regions in China.