A　trypsin　inhibitor　with　thermal　and　pH　stability,　designated　Mercine,　was　prepared　from　seeds　of　Glycine　max　(L.)　merr.　The　preparation　procedure　involved　ammonium　sulfate　precipitation,　ion-exchange　chromatography　on　CM-Sephadex　C-50,　affinity　chromatography　on　Affi-gel　blue　gel.　The　20　N-terminal　amino　acid　sequences　were　determined　to　be　DEYSKPCCDLCMCTRRMPPQ,　demonstrating　highly　homologies　with　the　sequence　of　Bowman-Birk　type　trypsin　inhibitors.　The　molecular　mass　and　isoelectric　point　of　the　inhibitor　were　estimated　by　SDS-PAGE　and　isoelectric　focusing　to　be　17.9　kD　and　4.6,　respectively.　Trypsin　could　be　completely　inhibited　by　Mercine　when　the　molar　ratio　was　8.0.　The　inhibitory　activity　of　Mercine　was　unaffected　after　exposure　to　temperatures　up　to　80C,　or　within　the　pH　range　2-12.　Besides　inhibiting　trypsin-chymotrypsin,　the　inhibitor　Mercine　demonstrated　additional　antifungal　activity　toward　the　species　of　Alternaria　alternate,　Fusarium　oxysporum,　Pythium　aphanidermatum,　Physalospora　piricola　and　Botrytis　cinerea.