A study was carried out from December 2009 to December 2013. About 300 specimens was collected in lower Saigon - Dongnai river system. The results showed that 81 species belonging to 56 general 32 families were recognized and classified. Gobid family (Gobiidae) was the most diverse group, with 16 species (19.75 percent of the total). Croakers (Sciaenidae) and Gouramies family (Osphronemidae) were the second-most diverse group, consisting of 6 species and account for 7.14 percent. The Sleepers family (Eleotridae) consisted of 6 species and accounted for 6.17 percent. Other families consisted 1-4 species, accounting for 1.23 - 4.94 percent. In the total of species classified, there were 38 migratory species, 35 economy valuable fish species, 2 species which are in Vietnam red list (2007, VU-Vulnerable).