Abstract: ObjectiveThe purpose of this paper was to illuminate the mechanism of exogenous substances on promoting nutrients uptake and utilization of tobacco, and provide reference for improving the exogenous root control technology based on quality and efficiency improvement for tobacco. MethodPot experiments were conducted. Conventional fertilizer (T1), and adding malic acid(T2), rooting powder(T3), sodium nitrophenolate and sodium alginate mixture(T4), Bacillus amy-loliquefaciens FZB42(T5) and expansin(T6) based on conventional fertilizer were set. No fertilization treatment for tobaccos was set as control(CK) to calculate fertilizer utilization rate. Dry matter of root, stem and leaf, as well as contents of nitrogen, phosphorus and potassium in leaf were measured at tobacco resettling, budding, and harvest over periods. Meanwhile, available nitrogen, available phosphorus and available potassium contents in soil were detected. ResultCompared with CK and T1, root growth rate was significantly(P<0.05, the same below) increased in T4, T5, and T6 during each growth period, dry matter accumulation of both root and ground plant, and nutrients(nitrogen, phosphorus and potassium) uptake were also increased. However, the proportion of tobacco leaf in total ground dry matter accumulation was decreased as growth periods advanced. Regression analysis showed that, root dry matter accumulation was significantly positively related to nitrogen(R2=0.87), phosphorus(R2=0.94), and potassium(R2=0.88) uptake from resettling to budding period(P<0.01). At this period, significant increasement of root growth rate was the key in exogenous substances promoting leaf nutrients uptake and utilization. T4 and T5 increased root growth rate by over 50%from resettling to budding period and significantly improved dry matter accumulation of tobacco. Leaf nitrogen uptake was increased by 46%and 66%, phosphorus uptake was increased by 77% and 118% and potassium uptake was increased by 58% and 69% respectively in T4 and T5. Conclu-sionConsidering stable effect and application security of tobacco root promoting , B. amyloliquefaciens FZB42 root-irriga-tion can be applied as a major regulation measure in Yuxi red-soil tobacco planting area.