The Kien Giang sea located on Thailand Bay is mostly unexplored where is anticipated to be able to provide a rich source of Actinobacteria, the prolific producers of antimicrobial secondary metabolites. Total 198 actinobacterial isolates were isolated from 63 sponge samples from 7 different sites in the Kien Giang Sea, Vietnam. Based on the ability of antimicrobial activity, 73/198 had against Salmonella typhimurium in which there were seven isolates with strong, 51 medium, and 15 weak resistances. Six best isolates (diameter of sterile ring >21 mm) were selected to identify by PCR 16S rDNA gene analysis and sequencing. The result showed that five strains characterized as Streptomyces spp., one strain belonged to genus Rhodococcus and Rhodococcus rhodochrous H2.6c strain was the highest antimicrobial activity to Salmonella typhimurium.