Abstract: Gracilaria blodgettii, a commercial red seaweed belonging to the Gracilaria and a material for agar extraction and abalone feeding, is currently cultured in ponds along the coast of southern China. In order to determine the optimum conditions for the growth of G.blodgettii, we studied the effects of different temperatures (18 ℃, 23 ℃, 28 ℃, 33 ℃ and 38 ℃), salinities (13, 18, 23, 28, 33 and 38) and light intensities (3 000 lx, 6 000 lx, 9 000 lx and 12 000 lx) on growth and biochemical constituents of G.blodgettii. The results show that the appropriate temperature, salinity and light intensity for its growth are 23~38 ℃, 18~38 and 6 000~9 000 lx, respectively. The optimum temperature, salinity and light intensity are 28~33 ℃, 23~33 and 9 000 lx, respectively. Under the optimum conditions, G.blodgettii suffered less from the damage of environment, having higher relative growth rate, the greatest content of phycobiliprotein and soluble protein, lower activity of peroxides (POD) and content of malondialdehyde and (MDA). The results suggest that the ability of physiological adjustment (increase in specific protein expression/ lower in hazardous substance) of G.blodgettii helps to resist high temperature and middle-high salinity.