Study on the effect of different salinities on the biological characteristics and population growth of brackish rotifer Brachionus plicatislis. In the first experiment, individual of rotifer which had been acclimated in different salinities was reared in 1 mL glass container in different salinity water (25?, 20?, 15?,10?, 5? and 0?). Rotifers were fed with 2.10⁶ cell/mL condensed Chlorella sp. which had been accustomed to respected salinities. The second one was performed in one litter system. Initial stocking density of rotifers was 200 ind./mL, feeding with Chlorella at 60,000 cells/ind./day and water exchange up to 30% every day. In 25? water treatment, rotifer had the longest lifespan (202.24±28.14 hours) and the highest fecundity (20.7 ± 2 eggs/individual). On the contrary, 0? treatment had the shortest lifespan (148.94 ± 16.84 hours) and the lowest fecundity (5.9 ± 0.74 eggs/individual). Density of rotifers was highest at 25? treatment  (2,873±199 ind.mL^-1) at the 6^th day and  2,280±151 ind.mL^-1 of rotifer population in freshwater. As a results, brackishwater rotifer B. plicatilis could growth in 0? water.