Abstract: Corn gluten peptides were prepared by four different kinds of proteases and their respective root-inhibiting activities on smoothscale kyllinga(Kyllinga brevitolia var.leiolepis) were evaluated in Petri dish bioassay when they were 0.5,1.0,2.0 and 5.0 mg·mL^-1 in concentration.Results show that they all demonstrated root-inhibiting activity,which increased with their concentration.Herbicidal activities of peptides prepared by alcalase and Papain were significantly higher than those prepared by flavourzyme and neutrase.The peptides varied in bioactivity with molecular weight.Peptides small in molecular weight(<5 000 u) exhibited higher herbicidal activity than those large in molecular weight.