The strain Ata28 of Bacillus subtilis i solated from tobacco leaves could obviously decrease the occurrence of Alternaria alternata , which was proved by the disease control experiment in greenhouse. After seed bacterization, the growth-promoting effect of Ata28 on tobacco seedling was tested in pot with aseptic soil, and the fresh weight above ground, leaf number, and the length and width of the biggest leaf of tobacco seedling were determined. The results indicated that the growth-promoting effect of Ata28 was significant. The difference between Ata28 treatment and the control was significant, it showed that the antagonistic bacterium Ata28 possessed both seedling growth-promoting and disease control effects.