Abstract: Some inducible antibacterial peptides were developed from the immunized haemolymph of Chinese oak silkworm ,Autheroca pernyi by injecting with Escherichia coll.Antibacterial peptid hed a strong inhibitory effect on the pathogen of rice leaf bacterial blight disease,Xanthomomas compestris pv aryzaeObservated the ultra structure of X.Oryzoe treated with antibacterial peptide by electromicroscope.The results showed the primary target of antibacterial peptide was against the membrane of cells,after 10-30 min the cell wall was be-stroied and the intercellular substances were pressed out of cell subsequently.Different ratio (1:10-200) mixture between the immunized haemolymph;suspension of X.oryzae(106cell/ml) were used to infect the leave of seedling or booting stage of rice.After 20 days,investigated the average lenght of leaf spot infection and counted with variance analysis.The results showed antibacterial peptide from immunized haemolymph had a distinct infectivity effect on the X.oryzae