Abstract: Both tobacco endophytic bacterium strain T295 and rhizobacterium strain R27 can effectively inhibit tobacco black root rot(TBRR). In order to analyze their control efficacy and mechanism, the synergism of T295 and R27 against TBRR and inhibition against hyphal growth and spore germination and effects on the activities of relative defensive enzymes, including phenylalanine ammonia lyase(PAL), peroxidase(POD), catalase(CAT), polyphenol oxidase(PPO)and superoxide dismutase(SOD)were determined. The results showed that the synergy of T295 and R27 improved apparently the control efficacy against TBRR and inhibited the hyphal growth of Thielaviopsis basicola(the pathogen of TBRR), but did not affect the inhibition of spore germination. The activities of PAL, POD, CAT, PPO and SOD in tobacco treated by T295 were higher than those treated by R27 and did not significantly differ from those treated by the mixture of T295 and R27. T295 and R27 did not present additive effect on the induced resistance, it indicated that the resistance of tobacco plants induced by the mixture mainly related to T295, which could promote the activities of relative defense enzymes in tobacco.