This study was conducted to investigate the effects of water temperature and fish size on feeding and growth of the lenok . The experimental fish of three sizes (7 g, 68 g, and 169 g) were reared at five water temperatures (6℃, 10℃, 14℃, 18℃, 22℃) using artificial diet. The results showed that the maximum feeding rate () was observed at 18℃ in small size, 14℃ and 18℃ in middle size, and 14℃ in large size () was obtained at 14℃ and 18℃ in small size and middle size, and at 14℃ in large size (<0.05). The maximum feeding rate and energy content of the lenok increased with increased fish size, however, the special growth rate decreased with increased fish size. Multiple regression model of SGR_w, of the lenok in relation to temperature and fish size was ln2-0.0157-0.0147T²-0.0021C_max and <0.05), while no interaction on SGR_w of the lenok between temperature and fish size was observed (>0.05). The results suggested that the optimum temperature for different fish sizes of the lenok was similar, which was between 14-18℃ based on maximum feeding rate (w).