Abstract: Fucoxanthin is a specific marine carotenoid with extensive bioactivities. Diatom is considered a potential industrial resource due to its rich fucoxanthin. The focus of commercialization is to establish high-yield strains and related extraction and culture accumulation conditions, but there is still lack of intensive understandings. This study selected the strain of Chaetoceros muelleri from 16 strains of marine diatom culture stock by comparing fucoxanthin content (ranged from 0.03 mg/g to 5.02 mg/g) and extraction efficiency (ranged from 1% to 89.78%). The experiment showed that, first, fucoxanthin changed strongly under different light intensities low: 50 μmol/(m²·s); medium: 100 μmol/(m²·s); high: 200 μmol/(m²·s), the highest content was obtained under low light intensity. Second, fucoxanthin content was higher in red light than in the blue light. Third, the change of fucoxanthin content is closely related with chlorophyll a and β-carotene. Under monochromatic light condition, the content of these photosynthetic pigments increased at late growth stage. These results indicated that strain and light selection can greatly increase the yield of fucoxanthin in the diatom.