Abstract: In order to select bio-organic fertilizer applied to tobacco plant root-zone, a pot experiment was conducted to study the effect of different bio-organic fertilizers applied to flue-cured tobacco root-zone on root morphology, root physiological characteristics and dry biomass of roots. The results showed that bio-organic fertilizers applied to root-zone could promote root length, root volume, root diameter, root branching number, improve root activity, increase dry biomass of roots. The "bio-organic fertilizer combined with 3 oil cake" was found to have the best effects of accelerating tobacco root growth. "Bio-organic fertilizer combined with 3 oil cake", "bio-organic fertilizer by tobacco straw fermentation" and "zhong-yan multi-effect bio-organic fertilizer" could be applied to flue-cured tobacco root-zone, while "embossed cudgel ore bio-organic fertilizer" could not be used for flue-cured tobacco root-zone application.