Mixed conifer-broadleaved plantations within a framework of close-to-nature forest management can be a good silvicultural alternative to large-scale monocultures of coniferous plantations in southern subtropical China. In 1993, monoculture stands of Pinus massoniana and Cunninghamia lanceolata were established on the Fubo Forest Farm, which is located in Pingxiang County of Guangxi. To improve the productivity of the coniferous plantation forest monocultures and maintain their ecological balance, close-to-nature silvicultural technology was employed in 2007-2008. In this process, the native species Castanopsis hystrix and Michelia gioii were interplanted in thinned P. massoniana and C. lanceolata stands (hereinafter referred to as the P. massoniana close-to-nature forest and the C. lanceolata close-to-nature forest), with a density of 405 trees/hm². In this study, P. massoniana and C. lanceolata plantation forest monocultures based on similarities in topography, soil texture, stand age, and management history were chosen as the reference to study the effects of close-to-nature transformation management in the early stages on the forest community structure and biodiversity, and soil properties, with the expectation of providing scientific reference points and a basis for the sustainable management of P. massoniana and C. lanceolata plantation forests. The results showed that: (1) The stand density and basal area of the P. massoniana and C. lanceolata close-to-nature forests were both significantly lower than those in corresponding plantation forest monocultures (P<0.05), but their average DBH was higher than in the plantation forest monocultures and the average DBH of P. massoniana was significantly different (P<0.05). (2) The stem number of adult trees (DBH≥10 cm) of the close-to-nature forests was lower than that in the plantation forest monocultures, and P. massoniana and C. lanceolata were still the dominant species, while the tree number and species number of trees (5≤DBH<10 cm) and young trees (1≤DBH<5 cm) of the close-to-nature forests were both higher than those in the plantation forest monocultures. The inter-planted C. hystrix and M. gioii turned out to be the young tree species with the highest importance value, and they grew better in the P. massoniana close-to-nature forest than in the C. lanceolata close-to-nature forest. (3) Species richness index, Shannon-Wiener index, Simpson index and Pielou index in the shrub and herbaceous layers of the P. massoniana close-to-nature forest were not significantly different from those in the P. massoniana plantation forest monocultures. The species richness index of the shrub layer and the Pielou index of the herbaceous layer of the C. lanceolata close-to-nature forest were significantly different from those in the C. lanceolata plantation forest monocultures (P<0.05) while the other indexes showed no significant differences. (4) Bulk density and total porosity in the soil profile, and soil total P, total N, total K and available K all showed no significant differences between the close-to-nature forests and the plantation forest monocultures, but the organic carbon content and pH value of the P. massoniana close-to-nature forest were significantly lower than those in the plantation forest monocultures (P<0.05), while soil available P in the C. lanceolata close-to-nature forest was significantly lower than in the plantation forest monocultures (P<0.05).