Objective To investigate the effect of supercritical CO₂ extraction on the removal of fat-soluble compounds from Sacharina japonica powder.Methods The process conditions for supercritical CO₂ extraction of S. japonica powder were optimized based on the defatting rate. Changes in volatile flavor compounds, fatty acid composition, and fucoxanthin content before and after the extraction process were analyzed using headspace gas chromatography-ion mobility spectrometry, gas chromatography, and high-performance liquid chromatography.Results The optimal conditions for supercritical CO₂ extraction were: extraction temperature of 50 ℃, extraction pressure of 45 MPa, and extraction time of 3 h, under which a defatting rate of 36.23% was achieved. A total of 70 volatile flavor compounds were identified qualitatively in S. japonica powder before and after extraction. Notably, the relative content of fishy or pungent odorants in the extracted powder was significantly reduced compared to the raw material, leading to a substantial improvement in overall flavor. Fatty acid composition analysis showed that the content of monounsaturated fatty acids was notably higher in the extracts, reaching (28.87±0.23)%, while the proportion of polyunsaturated fatty acids such as arachidonic acid (ARA) and eicosapentaenoic acid (EPA) increased to (37.72±2.36)% in the extracted powder. The fucoxanthin content in the raw S. japonica powder, extracted powder, and extracts were 0.050, 0.039, and 4.766 mg/g, respectively.Conclusion Supercritical CO₂ extraction can effectively remove volatile flavor compounds with fishy or pungent odors from S. japonica powder, while efficiently extracting and separating lipids and fucoxanthin.