To　explore　the　comprehensive　utilization　value　of　polysaccharides　from　Haematococcus　pluvialis　residue,　ethanol　gradient　precipitation　(40%,　60%　and　80%)　was　used　to　isolate　polysaccharides　from　H.　pluvialis　residue　in　this　study.　Three　fractions　with　crude　polysaccharides　(HP40,　HP60　and　HP80)　were　obtained　by　40%,　60%　and　80%　ethanol　precipitation　successively.　The　monosaccharide　composition,　molecular　weight,　structure,　particle　size　and　Zeta　potential　of　each　fraction　were　analyzed　by　high　performance　liquid　chromatography　(HPLC),　Fourier　transform　infrared　spectroscopy　(FT-IR),　high　pressure　gel　chromatography-multiple　angle　light　scattering　detector-differential　refractive　index　detector　(HPSEC-MALS-RI),　and　their　antioxidant　activity　was　also　evaluated.　Results　showed　that　the　physicochemical　properties　and　antioxidant　activity　of　polysaccharides　precipitated　from　H.　pluvialis　residue　were　significantly　affected　by　ethanol　concentration.　The　yield　and　purity　of　the　crude　polysaccharides　decreased　with　the　increase　of　ethanol　concentration.　Furthermore,　the　lower　molecular　weight　polysaccharides　were　precipitated　by　higher　concentration　of　ethanol.　High-purity　crude　polysaccharides　were　obtained　in　this　study,　in　which,　the　total　sugar　content　of　HP40　was　up　to　99.46%±0.015%.　All　fractions　contained　8　monosaccharides,　including　Glc,　Man,　Gal,　Ara,　Rha,　Xyl,　Fuc　and　Glc-UA,　while　the　composition　and　proportion　of　monosaccharides　were　different.　Compared　with　HP40,　ribose　was　also　involved　in　HP60　and　HP80,　which　contained　a　total　of　9　monosaccharides.　HP80　possessed　the　smallest　particle　size　(73.505±2.405　nm)　and　the　largest　Zeta　potential　absolute　value　(−11.6　mV).　The　results　of　antioxidant　analysis　showed　that　HP80　had　the　strongest　antioxidant　activity,　and　the　scavenging　rate　of　hydroxyl　radicals　was　up　to　96%　(10.0　mg/mL).　In　summary,　gradient　ethanol　precipitation　method　was　effective　to　isolate　polysaccharides　from　H.　pluvialis　residue　preliminarily,　and　obtained　polysaccharides　with　different　monosaccharide　composition,　particle　size,　molecular　weight　and　antioxidant　activity.　In　which,　the　highest　yield　and　sugar　content　was　gained　in　fraction　precipitated　by　40%　ethanol　(HP40),　while　the　smallest　molecular　weight　and　the　strongest　antioxidant　capacity　were　gained　in　fraction　precipitated　by　80%　ethanol　(HP80).　©　The　Author(s)　2025.