Twelve field surveys were conducted in 2012 to collect the samples of zooplankton at 11 sites in the lower area of Long An province. the authors recorded a total of 76 species belonging to nine groups: Protozoa, Rotifera, Cladocera, Copepoda, Ostracoda, Decapoda, Chaetognatha, Chordata, and Larvae. Of which Copeoda, Nauplius, and Copepoda are three most diverse and abundant groups. The most common species recorded in the study area are Acartia pacifica, Acartiella sinenssis, Oithona simplex, Paracalanus parvus, Pseudodiaptomus incisus, and Copepoda nauplius.