Abstract: In order to determine the colonization of endophytic bacterium YN201448 in tobacco, we successfully obtained a stable GFP tagged strain 48-pGFP by transferring the pGFP4412 plasmid into YN201448 via natural transformation. 48-pGFP showed the same antagonistic effect against 5 pathogenic fungi as the wild strain YN201448. 48-pGFP was observed to be distributed in root, stem and leaf tissues of tobacco after its seeds soaked and seedling roots drenched with 48-pGFP. The colonizing bacterium decreased with the trend of root > stem > leaf, and 48-pGFP could colonize in rhizospheric soil stably. Fluorescence microscope observation indicated that 48-pGFP mainly appeared in tobacco stem epidermis, cortex and vascular tissue cells. Therefore, YN201448 could colonize inside and around tobacco plant stably for a relatively long period of time.