Total of 68 bacterial isolates inside the roots of Bruguiera and Ceriops in mangrove forest of Soc Trang province, Vietnam. They were isolated from 16 root samples on the two kinds of Burk’ N-free and NBRIP semi-solid medium with the presence of pellice located below the surface of medium 1-2 mm as indicator. Almost their colonies have round-shaped; milky, white clear (on Burk’s medium) and yellow (on NBRIP medium); entire or lobate margin; diameter size of these colonies varied from 0.2 to 3.0 mm and all of them are Gram-negative by Gram stain, motility. 38/68 isolates grew on NBRIP medium and 30/68 isolates grew on Burk’s N-free medium and all isolates did not produce siderophore. From 68 isolates, screening of 6 isolates had high nitrogen fixation ability, 8 isolates insolved high phosphate and 9 isolates biosynthezed high IAA concentration in NBRIP tryptophan-free liquid medium; in Burk’s N-free without tryptophan medium, selecting of 11 isolates had high phosphate solubilization ability and 8 isolates biosynthezed high IAA concentration. Nine good isolates were selected to identify, sequencing and compared with bacterial 16s-rRNA genes in Genbank using BLAST N software. The results showed that 9 strains belonged to 7 genera as Mangrovibacter, Acinetobacter, Gallaecimonas, Martelella, Stenotrophomonas, Curtobacterium and Defluviimonas with 99% similarity