Eucalyptus is one of the world's most widely planted tropical and sub-tropical fast-growing hardwoods, which has extremely high economic value. Plantations of eucalyptus have been extensively established in South China during the past decades. However, there is an ongoing debate concerning the environmental effects and the development of eucalyptus plantations in South China. The ecological/environmental effects of eucalyptus plantations need to be further studied. This study contraposed the potentially ecological problems of typical eucalyptus in South China, selected three types of plantations including 10 species mixed plantation (10S), 30 species mixed plantation (30S), and eucalyptus monoculture (E), and established two treatments of eucalyptus cutting (EC) and eucalyptus cutting with understory removal (ECUr) in the eucalyptus monocultures. The influences of eucalyptus management on soil physical and chemical characteristics, soil microorganisms and nematode communities were analyzed by comparing the differences in soil physical and chemical properties and biological indicators under different forest types and management measures. The results showed that there was no significant difference in soil physico-chemical properties among the three plantation types. However, the soil fungal biomass, the ratio of fungal biomass to bacterial biomass, and the bacterivorous nematode abundance of the eucalyptus monoculture were significantly higher than those of the 10 and 30 species mixed plantations. Besides, the nematode diversity and fungivorous nematode abundance of the eucalyptus monoculture were apparently higher than those of 10 species mixed plantation. Under different eucalyptus forest management measures, the eucalyptus cutting treatment did not significantly affect the soil physico-chemical and biological properties. But the eucalyptus cutting with understory removal treatment remarkably reduced the soil water content, the ratio of fungal biomass to bacterial biomass, the abundances of total nematodes, bacterivorous nematodes, fungivorous nematodes and omnivorous-carnivorous nematodes. The results indicated that the eucalyptus monoculture had generally better soil physico-chemical and biological characteristics than the mixed plantations of native species at the same age. In other words, the soil quality of the eucalyptus plantation was not lower than the mixed plantations. Our results also indicated that eucalyptus cutting decreased the soil quality, particularly when the understory was removed. Overall, the eucalyptus plantations could be beneficial to the environment when used as a measure of ecosystem restoration. As an economic tree species, however, unreasonable management practices of eucalyptus plantations may induce severe soil degradation, such as soil erosion, nutrient depletion, biodiversity loss, and production decline. Therefore, the trade-off between ecological and economic benefits of the eucalyptus plantations may need to focus on forest management measures in the future.