China has the world's largest total area of plantation resource, among which the most common species is masson pine (Pinus massoniana Lamb). As a pioneer tree species in hill areas of southern China, masson pine is highly resistant to drought and infertile soils and thus plays an important role in the ecological restoration. However, as most masson pine plantations are monocultures, consisting of a single dominant tree species, their ecosystem services are often poor. Close-to-nature management is of great significance for the increase of species diversity and the improvement of ecological service in plantations. In 2005, a thinning experiment was conducted in a 12-year-old masson pine plantation in the Experiment Center of Tropical Forestry of Chinese Academy of Forestry, with four different levels of thinning density (i.e. 50%, 40%, 30%, and 20%). Then, four native broad-leaved tree species, ie. Castanopsis fissa, Mytilaria laosensis, Machilus pingii and C. hystrix, were interplanted with a density of 120 trees/hm² in the thinned masson pine plantation. We investigated the community species diversity and growth conditions before the thinning experiment. Five years later, a re-investigation of the plots showed that: (1) the number of tree layer species were significant increased, with the species richness per plot (600 m²) from 2.75±2.56 to 11.17±4.32 and individual number from 5.75±2.56 to 32.17.17±19.09. In addition to the original dominant species before the experiment, nearly 10 species in original shrub layer grew into tree layer, including Evodia lepta,Schefflera minutistellata,Styrax faberi,Macaranga denticulata,Ficus esquiroliana,Eurya ciliata,Diospyros morrisiana,Pithecellobium clypearia,Litsea pungens and Actinodaphne pilosa. (2) the number of shrub and herb layer species increased only slightly from 24.63±4.24 to 27.58±3.80 per plot (600 m²). Different thinning density treatments had no significant effect on shrub-herb species in terms of Species richness index, Shannon-Wiener index, Simpson index, and Pielou index. The dominant species in shrub and herb layer were Evodia lepta and Cyrtococcum patens, respectively, which are similar with those before the thinning experiment. (3) The saplings of broad-leaved tree species benefited greatly from thinning management. The height and DBH increased significantly with the thinning intensity in Castanopsis fissa and C. hystrix. In the 50% thinning intensity stands, the broad-leaves tree saplings had significantly better performance than those in other stands, suggesting that the 50% thinning management was optimal for the growth of broad-leaves tree species. (4) There were significantly differences in early growth among the four broad-leave tree species in masson pine plantation. Overall, the early growth rates of C. fissa and Mytilaria laosensis were obviously higher than the other two species. Our results highlight the significant effects of close-to-nature management, i.e. thinning of dominant masson pine and interplanting of native tree species, on the increase of species diversity in plantations even in a relative short experimental period. As higher levels of species diversity are essential for community stability (e.g. the resistance of forest to variable disturbances), the close-to-nature management will benefit the supply of high-quality timbers and ecological services in masson pine plantations.