The　optimization　of　the　extraction　process　of　protein　from　Chlorella　vulgaris　was　achieved　by　response　surface　methodology　and　its　antioxidant　activity　were　characterized.　Chlorella　protein　extraction　rate　was　taken　as　the　index　to　study　the　effect　of　p　H,　ratio　of　liquid:　material　(V/m),　extraction　time,　tween　concentration　and　ultrasonic　time　on　extraction　yield.　On　the　basis　of　single　factor　experiment,　the　three　factors　and　three　levels　of　response　surface　analysis　method　was　taken　to　determine　the　Chlorella　protein　extraction　process.　The　results　showed　that　a　p　H　of　8.0,　a　extraction　time　of　6　hours　and　a　tween　concentration　of　0.1%　were　optimal　for　protein　extraction　from　Chlorella　and　the　extraction　ratio　was　46.39%.　The　concentration　for　50%　of　maximal　effect　(EC50)　of　Chlorella　protein　extracted　under　the　optimal　condition　to　DPPH　free　radicals,　superoxide　anion　radicals　and　ABTS　radicals　were　1.40　mg/m　L,　1.45　mg/m　L　and　16.6　μg/m　L,　which　showed　that　protein　extraction　from　Chlorella　vulgaris　has　certain　antioxidant　activity.　©　2018,　Editorial　Office　of　Journal　of　CIFST.　All　right　reserved.