The farming of clam Meretrix lyrata has been successfully developed since 1987 and brought high economic and social benefits to the coastal communities. Because of it being a highly valued fishery resource especially in Vietnam, recently, Meretrix lyrata has become another new species with a large-scale farming potential and market prospects in the South China Sea. In this study, effects of various seawater temperatures and salinities on the survival and growth of juveniles of Meretrix lyrata were investigated by adopting indoor control measures, which would provide both insight into ecology of juveniles and reference for culturing and spreading of M. lyrata. The results showed that the suitable sea water temperature for the survival of M. lyrata juveniles was 12.2-35.6℃, and the optimum sea water temperature was 24-30℃; In addition, the suitable and optimum sea water temperatures for the growth of M. lyrata juveniles were 23.5-330℃ and 27-30℃ respectively, suggesting that M. lyrata be typical of the South intertidal shellfish. On the other hand, the suitable sea water salinity and the optimum salinities for the survival of M. lyrata juveniles were 4.3-40.5 and 11-31 respectively, showing that M. lyrata was typical of the euryhaline intertidal shellfish. Furthermore, the suitable and optimum sea water salinities for the growth of M. lyrata juveniles were 17.1-33.4 and 19-23 respectively, When sea water salinity was in optimal range, shell length, shell height and fresh weight of M. lyrata juveniles presented higher growth rates. Out of this range, however, growth rate of each character of M. lyrata juveniles was significantly decreased, suggesting that the culture area of M. lyrata should be in the low tide zone, and the estuarine area of the low salinity should be avoided for practical use. Lower and upper sensitive incipient temperatures were 21℃ and 33℃ respectively, and lower and upper sensitive incipient salinities were 9 and 33 respectively. M. lyrata juveniles possessed tolerance to temperature and salinity to some extent. The relative survival rate of M. lyrata juveniles was 100% at 37℃ for 6d, but all died at 39℃ and 41℃ for 3d and 5d respectively. At 4℃, 6℃, 8℃, 10℃ and 12℃, the time for 100% survival of M. lyrata juveniles was 3d, 4d, 6d, 9d and 11d respectively, showing that culture management of M. lyrata should be strengthened in winter or summer to prevent sudden changes of sea water temperature because the South China Sea is subjected to lasting low temperatures in winter owing to strong cold weather, as well as the effect of persistent high temperature in summer. When the salinity was 0,5,7 and 9, M. lyrata juveniles showed 100% survival for 5d,8d,10d and 10d respectively, whereas the salinity was held at 33,35,37 and 39, M. lyrata juveniles maintained 100% survival for 7d,5d,3d and 3d respectively. However, death occurred with M. lyrata juveniles when the salinity was 41. Therefore, M. lyrata juveniles possessed short-term tolerance to extreme low or high salinity.