Saltwater intrusion in the Mekong delta is increasing each year. It affects the longevity and reproduction of freshwater aquatic species, especially zooplanktonic species. This study aims to identify the appropriate salinity range for the growth of Moina sp. The study was arranged with two experiments, including determining the salinity tolerance range of Moina and the effect of salinity on their reproductive pattern and biomass production. The results show that the Moina sp. population grew and developed well in salinity of 1‰, but the population died off when the salinity increased to 7‰. Reproduction of Moina sp. was not affected at 3‰, but the longevity of Moina sp. was reduced, leading to a reduction in population. Moina sp. tended to produce high levels of resting eggs at 5‰ salinity.