The effort of proteolytic enzyme on the absorption and excretion of sulfadimethoxine are investigated in this paper. The rat small intestinal absortion of sulfadimethoxine in the presence of proteolytic enzymes such as chymotrypsin and trypsin are increasingly absorbed more than 20% during 3 hours. Blood levels of sulfadimethoxine following oral administration are not effected by proteolytic enzyme, but both on the high concentration of chymotrypsin and the low concentration of trypsin at only 3 and 4 hours are increased(P<0.05) from that of the control . Blood levels of sulfadimethoxine after duodenum injection are remakably enhensed to correspand to 18.5-25.0% (P<0.01) by the proteolytic enzyme concentration respectively. Proteolytic enzymes did not give influence on excretions of sulfadimethoxine after duodenum and oral administration.