The effects of high temperature stress and two different body sizes on growth performance of olive flounder was studied in laboratory conditions. The temperature of 25 ℃ was performed as control, and the temperature of 28 ℃, 30 ℃ and 32 ℃ were as high temperature stress groups. The experiments included experiment I and experiment II. The results were as follows: (1) the survival rates of olive flounder were nearly 100% when the temperature was between 25 to 30 ℃, while the survival rates of olive flounder decreased significantly at the temperature of 32 ℃. The survival rates of two differernt body sizes of flounder have no significant differences at the temperature of 32 ℃ (P<0.05）. (2) Water temperature significantly affected the growth of two different sizes of fish, and a quadratic regression was fit to describe the relationship between the SGR, FR, FCE and the water temperature (Oneway ANOVA, P<0.01）. (3) Compared with growth performance of different sized fish at the same temperature, the SGR and FR of experiment I were remarkably higher than those of experiment II （P<0.05）, while the FCE of experiment I was significantly lower than that of experiment II（P <0.05）, which indicated that body size have a significant effect on growth performance of olive flounder. The result of present study indicated that the temperature of 32 ℃ may be the upper limit of olive flounder, and the high temperature stress and body size have a significant effect on the growth performance of olive flounder.