The study was conducted on the copepod Schmackeria dubia to investigate their tolerance and cyst production potential under changes of environmental factors (temperature, salinity) and feeding regimes. S. dubia were arranged in one liter beaker system at density of 50 copepoda/L in 500 mL prepared sea water. The copepods were fed with Chaetoceros calcitrans at 500,000 cells.mL^-1. In the first experiment, S. dubia were subjected to four different feeding regimes including (i) none fed, (ii) fed 25%, (iii) fed 50%, and (iv) fed 100% (Control). Each treatment was replicated 4 times. In Experiment 2, S. dubia were exposed to different salinities including 20, 30, 40, 50, 60 and 70?. Similarly, S. dubia in Experiment 3 were subjected to different temperature of 30^oC, 32^oC, 34^oC, 36^oC, 38^oC và 40^oC. Densities of S. dubia were checked daily and cysts were checked at the end of experiments. The results of the first experiment showed that S. dubia population did not grow well in lower amount of feed treatments. In none fed treatment, S. dubia died off after 7 days. Growth of S. dubia population in  25% and 50% fed treatments was lower than that in 100% fed treatment. In the second experiment, S. dubia population grew best at 20? with  1282±45 ind.L^-1 at day 21. The population grew slowly at higher salinity and died off at 50, 60, and 70?. The third experiment showed that growth of S. dubia population decreased when temperature increased as 34, 36, 38 and 40 ºC. Best growth was found in 30^oC treatment. There was no any cyst found in all experiments and treatments in their unfavorable conditions.