The growth dynamics of different tree species interplanted under Pinus massoniana with four thinning intensities were investigated in order to determine the suitable intercropping species in various types of stand structure, which will provide a technical support for the close-to-natural management of Pinus massoniana plantation. Fifteen-year-old Pinus massoniana plantation was thinned in February 2008 and the reserved densities were 225 (I), 300 (II), 375 (III) and 450 (IV) stems per hacter, respectively. Five indigenous broadleaf species were then interplanted meanly under the Pinus massoniana plantation and the diameter at breast height (DBH) or root collar diameter, tree height and crown width were investigated every two years for eight consecutive years since 2008. The analyses of variance and Duncan multiple’s comparison were conducted to examine the growth dynamic response of intercropped tree species to the thinning intensity. There was significant effect of thinning intensity on the growth of understory interplanting broad-leaved tree species. For example, the DBH, tree height and crown width of Quercus griffithii and Manglietia glauca, and the DBH and crown width of Castanopsis hystrix decreased significantly with the increase of reserved density, while the tree height of Castanopsis hystrix and Erythrophleum fordii were little influenced by the thinning intensity. The DBH and crown width of Erythrophleum fordii, and tree height and crown width of Michelia hedyosperma were also declined with the increase of reserved density although the thinning intensity had no significant influence on the growth initially. Contrarily, the DBH of Michelia hedyosperma increased with the increasing reserved density. Additionally, the DBH, tree height and crown width of Quercus griffithii, the tree height and crown width of Manglietia glauca, and tree height of Castanopsis hystrix reached the maximum at the third year after interplanting, while the DBH of Castanopsis hystrix, Manglietia glauca and Michelia hedyosperma reached the peak value at the fifth year after interplanting. The DBH, tree height and crown width of Erythrophleum fordii, the tree height and crown width of Michelia hedyosperma, and the crown width of Castanopsis hystrix peaked at ninth year after interplanting. Among the broad-leaf tree species interplanted under the Pinus massoniana plantation after thinning, the best growth was Quercus griffithii, followed by Castanopsis hystrix, Manglietia glauca, Michelia hedyosperma and Erythrophleum fordii. The growth of Quercus griffithii, Castanopsis hystrix and Manglietia glauca increased as the thinning intensity increased, while the growth of Michelia hedyosperma and Erythrophleum fordii were not significantly affected by the thinning intensity. The result suggested that Quercus griffithii, Castanopsis hystrix and Manglietia glauca were suitable intercropping species in the thinning intensity (I, II) and the Michelia hedyosperma and Erythrophleum fordii were suitable intercropping species in the thinning intensity (III, IV) of fifteen-year-old Pinus massoniana plantation in southwest Guangxi.