On　the　basis　of　single　factor　experiment,　the　extraction　process　of　Gelidium　amansii　ethanol　extract　(GAEE)　was　optimized　by　response　surface　methodology.　Then,　the　GAEE　was　successively　extracted　by　petroleum　ether,　ethyl　acetate　and　n-butanol,　and　the　antioxidant　and　antibacterial　activities　of　different　extraction　phases　were　evaluated.　The　results　showed　that　the　optimum　extraction　conditions　were　as　follows:　extraction　time　was　64　min,　ultrasonic　power　was　350　W,　extraction　temperature　was　55　!,　ethanol　concentration　was　60%　and　solid-liquid　ratio　was　1:35.　The　extraction　rate　of　GAEE　was　1.654　g/g,　and　DPPH　radical　scavenging　rate　of　GAEE　(2　mg/mL)　was　58.29%　Subsequent　experiments　proved　that　the　antioxidant　and　antibacterial　activities　of　different　extraction　phases　were　concentration　dependent,　and　the　antioxidant　and　antibacterial　activities　of　ethyl　acetate　phase　were　the　strongest.　IC50　values　of　ethyl　acetate　phase　against　DPPH,　ALTS　free　radicals,　and　hydroxyl　radical　were　672.4,　14.1,　599.7　μg/mL　respectively.　Their　minimum　in　hibitory　concentrations　(DIC)　of　ethyl　acetate　phase　against　Staphylococcus　aureus　and　Vibrio　parahaemolyticus　were　156.3,　156.3　μg/mL,　and　the　minimum　bactericidal　concentrations　(DLC)　of　ethyl　acetate　phase　against　Staphylococcus　aureus　and　Vibrio　parahaemolyticus　were　625,　312.5　μg/mL.　©　2023　Chinese　Institute　of　Food　Science　and　Technology.　All　rights　reserved.