A protease that plays a role on autolysis of Antarctic krill was purified from Antarctic krill and its major physical and chemical characteristics were studied.The purified protease was obtained after 30% ~ 70% ammonium sulfate grading precipitation,DEAE-Sepharose Fast Flow anion-exchange chromatography and Sephacryl S-200 HR chromatography.The protease was confirmed by a single band on SDS-PAGE and was purified by 12.59-fold with the yield of 43%.The relative molecular mass of the enzyme was determined to be about 28 ku.The casein was used as substrate to measure the characteristics of the protease.The optimum pH and temperature of the enzyme were 8.0 and 50 ℃,respectively.The enzyme was stable when pH value is in the range of 7.0 to 9.5 and the temperature is blow 45 ℃;PMSF(phenylmethyl sulfonyl fluoride),SBTI(strontium bismuth titanate) and TLCK(N-α-Tosyl-L-Lysine Chloromethyl Ketone) can obviously inhibit the enzyme.