Tea　dregs　possess　abundant　proteins,　and　the　objective　of　this　study　was　to　investigate　the　antioxidant　activity　of　tea　dregs　protein　hydrolysate　with　limited　hydrolysis　by　protamex　and　its　possible　action　mechanism.　Tea　dregs　protein　was　hydrolysed　by　alcalase,　protamex　or　neutrase.　The　hydrolysis　condition　was　optimised,　and　the　hydrolysate　was　characterised　for　1,1-diphenyl-2-picryl　hydrazyl　(DPPH)　radical-scavenging　activity,　hydroxyl　radical-scavenging　activity　and　antioxidant　activity　in　linoleic　acid　(LA)　system　and　in　chicken　products.　Tea　dregs　protein　hydrolysate　(TDPH)　was　formulated　(0.1%,　0.5%,　1.0%,　w/w)　into　chicken　products　to　determine　in　situ　antioxidant　efficacy.　Thiobarbituric　acid-reactive　substances　(TBARS)　and　peroxide　value　(POV)　formed　in　chicken　products　during　storage　(4　°C,　0-7　days)　were　analysed.　Results　showed　that　the　optimum　hydrolysis　condition　was　at　50　°C,　pH　7.0　for　20　min,　and　the　concentration　of　tea　dregs　protein　was　1.5%;　ratio　of　protamex　to　substrate　was　6000　U　g　-1.　The　radical-scavenging　ratio　of　TDPH　to　1,1-diphenyl-2-picryl　hydrazyl　(DPPH)　was　90.30%　at　the　concentration　of　0.1　mg　mL　-1　and　that　to　hydroxyl　radical　was　65.18%　at　the　concentration　of　1.0　mg　mL　-1.　Moreover,　it　also　showed　strong　antioxidant　activity　both　in　linoleic　acid　(LA)　system　and　in　chicken　products.　The　molecular　weight　distribution　of　tea　dregs　hydrolysates　was　determined　by　nanofiltration　tubular　membrane,　and　the　protein　hydrolysates　with　molecular　weight　above　8000　Da　had　more　effective　antioxidant　activity.　The　radical-scavenging　activities　to　DPPH　and　hydroxyl　radical　were　85.72%　at　0.1　mg　mL　-1　and　71.52%　at　1.0　mg　mL　-1,　respectively.　These　findings　suggest　that　the　enzymatic　hydrolysate　of　tea　dregs　protein　probably　possesses　the　specific　peptides/amino　acids　which　could　stabilise　or　terminate　the　radicals　through　donating　hydrogen.　In　addition,　the　hydrolysate　could　form　a　physical　barrier　around　the　fat　droplets.　©　2014　Institute　of　Food　Science　and　Technology.