The effects of different rearing temperature on growth and survival rate of hard clams were investigated. The small (4.31 ± 0.27 mm), moderate (11.86 ± 0.65 mm) and large (20.63 ± 0.53 mm) sizes of hard clams were used in this study. These hard clams were rearing at 5 different temperatures, i.e., 15, 20, 25, 30, and 35°C in FRP tanks. The rearing salinity was 15-18 ppt. The duration of the experiment was 120 days. For small size group, the clams had higher growth rate at 30 and 35°C, but the survival rates were low (10-20%). The survival ratse of hard clams cultured at 15°C, 20°C, and 25°C were over 70％. The largest biomass revealed at 20°C and 25°C. The optimal rearing temperatures were 20°C and 25°C for small size hard clams. For moderate and large size groups, growth rate increased with increasing rearing temperature. Low rearing temperature had higher survival rate (over 90%). However, moderate and large size clams cultured under low temperature had high survival (about 90％). The optimal rearing temperatures for moderate and large size clams were 15-35°C.