Gelatinous zooplankton are recognized as key components of aquatic ecosystems, and their outbreaks have been examined in recent years. The moon jellyfish Aurelia coerulea is one of the most common gelatinous zooplankton inhabiting many parts of the world's coastal waters, and outbreaks of this species have been reported from various regions. A key step toward better knowledge of the causes and mechanisms of mass occurrences in scyphozoan jellyfish is to assess the extent of environmentally-induced effects on the phenotype of different phases in their complex life cycle. Moon jellyfish Aurelia coerulea has been reported to have high mortality during the ephyra stage, which potentially affects the population size of the later medusa stage. The effects of the physical environment, especially temperature and salinity, are even more unclear. Laboratory experiments were carried out to quantify the extent of environmentally induced changes in Aurelia coerulea ephyrae morphology, and subsequent effects on ephyrae growth and survival, in response to temperature and salinity. We tested the effects of temperature (2.5, 5, 7.5, 10, 15, 20, 25, 27.5 and 30 ℃) and salinity (15, 20, 25, 30, 35 and 40) on the survival and growth under control conditions. The experiment lasted for 30 days. Results showed that both temperature and salinity significantly affected the ephyrae development, growth and survival. In the salinity 15-35, the ephyrae could survival under 2.5-25℃, and grow in 15-25℃.The suitable temperature and salinity for the survival and growth of the jellyfish ephyrae was 20-25℃ and 20-30. The bell diameter of ephyrae at 20℃ and 25 was the highest. Compared with the salinity, the effect of temperature on the survival and growth of ephyrae was more significantly. In the salinity of 15-35, the bell diameter of ephyrae increased with the temperature increased and the duration of development shortened and mortality decreased as the temperature increased in 2.5℃ to 25℃.There were significant interactions between temperature and salinity on the ephyrae, which manifested as with the temperature decreasing, the adaptability of ephyrae to higher salinity was enhanced. The results showed that in salinity of 40, the survival of ephyrae in lower temperature groups (2.5-15℃) were higher than those in higher temperature groups (20-30℃). In temperature 5-15 ℃, the specific growth rate of ephyrae was higher in salinity of 35 than those in other salinity groups, whereas the highest special growth rate was in salinity of 20 under the temperature groups 20 and 25℃. The suitable temperature and salinity in the field would therefore elevate ephyrae survival rate, accelerate individual development, and thus ensure the population size of medusae. The results will play a very important role in making clear the seasonal dynamic changes of ephyrae population and revealing the outbreak mechanism.