Abstract: By taking Thalassiosira weissflogii as the raw material,the effects of different concentrations of nitrogen and phosphorus nutrients on the growth and accumulation of fucoxanthin in algae were studied in this paper.Under different conditions,the cell density curve was drawn by sampling during the growth,the biomass was measured at the later growth stage,and the fucoxanthin was extracted with organic solvent and detected by the HPLC.The results showed that compared with other nitrogen nutrient treatments,urea group with 0.882 mmol·L^-1 concentration was the most suitable for the growth and fucoxanin accumulation of T.weissflogii,and there were significant differences(P＜0.05).There was no significant difference in biomass accumulation of 0.054 mmol·L^-1 KH₂PO₄ group,but there was a significant difference in fucoxanthin content accumulation compared with other phosphorus nutrients(P＜0.05).Under the condition of nitrogen or phosphorus deficiency,the growth and the accumulation of fucoxanthin in T.weissflogii were seriously affected.This study provided a theoretical basis for the optimization of culture medium and the high yield of fucoxanthin in T.weissflogii.