Abstract:In order to accelerate the growth of Parashorea chinensis seedlings, the Bacillus agents and dosage were selected. The seedlings at 1.5-year old were treated with different concentration Bacillus agents, including B. mucilaginosus, B. laterosporus, and B. megaterium, respectively. The results showed that the growth and photosynthetic indexes of seedlings were improved by three Bacillus agents. Compared to CK (irrigated only with clean water), the height and diameter increment of P. chinensis seedlings increased by 30.2%-57.2% and 5.3%-49.7%, the root activity increased by 74.5%-227.4%, while the net photosynthetic rate increased by 15.3%-227.6%. The seedling height, ground diameter, biomass, root surface area, root average diameter, leaf area and chlorophyll content were the highest under the treatment of 6.0×109cfu/g B. megaterium, as well as the net photosynthetic rate, ФPSⅡ and qP, which were consistent with the results of seedling quality index and membership function method. Therefore, Bacillus megaterium at 6.0×109 cfu/g was the most beneficial microbial agent to improve the growth and development of P. chinensis.