Transforming Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) forest into precious indigenous broadleaf forest can not only provide high-value wood, but also enhance ecosystem service function, which is one of the most promising management measures of transforming the degraded coniferous forest in China. These transformations can alter the canopy structure community and the physicochemical properties of soil which caused by the quantity and quality of the litterfall. However, the impacts and mechanisms of broadleaf transformation on the species composition and diversity of undergrowth plant are still poorly understood. In this research, the replanted Chinese fir forest, Castanopsis hystrix forest and Mytilaria laosensis forest on the cutting-blank of the Chinese fir forest in south subtropics of China were studied. And its plant species composition and diversity in the shrub and herb layers were investigated. Our observations confirm that:(1) compared with Chinese fir, the richness and diversity of plant species in shrub layer of reconstructive C. hystrix forest and M. laosensis forest were extremely significant declined (P<0.01), while only the richness in herb layer extreme decreased significantly (P<0.01), and the diversity of the three forest types did not change distinctly (P >0.05). (2) Principal component analysis (PCA) showed that the composition of plant species in the shrub layer and herb layer of the transformed stand changed significantly. Redundancy analysis (RDA) determined that the main reason for the changes of the plant species composition in shrub layer was the obvious change of the canopy light transmittance, C/N ratio of soil, soil water content and C/N ratio of litterfall after the transformation of Chinese fir forest into C. hystrix forest and M. laosensis forest. The marked changes of canopy light transmittance and C/N ratio of soil were the main factors which led to the significant variation of plant species composition in the herbaceous layer under the forest types. (3) The variance partitioning showed that the independent effects of microtopography, tree features and soil physical-chemical proprieties had higher effects on plant species composition of shrub layer and herb layer than their interaction effects. Therefore, it is important to adjust the density and improve the canopy structure of the forests appropriately, and ultimately provide more opportunities for the invasion, settlement, reproduction and regeneration of more understory plant species when transforming Chinese fir into precious indigenous broadleaf forest. This study provides scientific basis for the operating management and improving of the multi-functional ecosystem of the plantation forests in subtropical China.