Abstract: To better protect herb bio-diversity, the relationships between the growth of Pinus massoniana, herb bio-diversity and terrains were studied by field investigations, calculation and analysis. The results showed that: (1) there were significant and highly significant correlations among Pinus massoniana growth factors such as height, DBH (diameter at breast height), under crown height, canopy size and slope (P＜0.05 or P＜0.01); (2) in terms of correlation coefficients, the effect degree of Pinus massoniana growth factors on herb biodiversity followed an order as canopy (-0.911**)＞under crown height (-0.645**)＞DBH (-0.608*)＞height (- 0.555*) ＞canopy size (- 0.200) (*P＜0.05; **P＜0.01); (3) there were highly significant and significant correlations between ecological factor such as slope position and Margalef richness index (R) or Simpson index (D), indicating that the slope position was the main ecological factor affecting undergrowth herb diversity of Pinus massoniana in Dajiang Forest Farm of Qiyang County. All the results indicated that timely tending and thinning of Pinus massoniana and appropriate plantation of herb under layer could increase undergrowth herb bio-diversity, and in favor of the protection and sustainable utilization of undergrowth bio-diversity.