Abstract: Taking S180-bearing mice and EAC-bearing mice as animal models,the antibacterial peptide (ABP) purified from the haemolymph of the silkworm (Bombyx mori) pupae was used to investigate the effects against the turmor in vivo.The results showed the ABP significantly inhibited turmor weight.The inhibitory rate of ABP at dose of 3792,4542,4980 U·(0.5 mL·20 g·d)-1×10 d,I.p.were 42.86%,39.13% and 37.89% respectively.ABP had no inhibitory effects on the number of leukocytes.Histopathological assay showed that ABP induced tumor tissue necrosis in large scales and there were lots of inflammatory cells (monocytes,neutrophils and lymphocytes) around tumor cells.It also could obviously reduce EAC peritoneal ascites fluid.