Abstract: The existence and function of endophytic bacteria have been widely recognized with the in-depth study of plant micro- ecosystem. The number of endophytic bacteria in different organs has significant differences. Endophytic bacteria in plant roots are much more abundant than those in other plant organs, and they have the host and species characteristics, which are caused by the coefficient complex influences of biotic and abiotic factors. Endophytic bacteria can colonize in the host plant roots from rhizosphere through many media, such as wind, soil particles, water, agriculture machinery, human, bird, insect and elegans and so on. They also play diversified roles in plant growth, such as solubilizing phosphate, producing of plant hormone, fixing of nitrogen, synthesizing the siderophores, inducing plant resistances and antagonism against pathogen fungi and so on. In order to understand the resources of endophytic root bacteria and provide a reference for development and utilization, the authors reviewed the diversity of root bacterial endophytes, the process of their colonization, the growth promoting activity and their potential applied prospects in this paper.