Abstract: We studied the effects of different temperature, salinity, light intensity, nutrient mass ratio and water depth on growth and photosynthetic pigments of seedlings of Sargassum mcclurei. The main results are as follows: the suitable temperature and salinity for S.mcclurei growth are 12~20 ℃ and 22~28, and the optimal growth temperature and salinity are12 ℃ and 28, respectively. Resistance and decay of seedlings occur when the temperature is above 24 ℃ or the salinity below 13. Seedlings grow quickly under 1 000~3 000 lx light intensity; but when the light intensity is too high, seedlings rot. The suitable nutrient mass ratio and water depth for S.mcclurei are m(NaNO₃) : m(KH₂PO₃)=15 : 1 and 30 cm, respectively, while water depth above 60 cm inhibits its growth.