Abstract: Bismerthiazol bactericide showed its protective and curative efficacy on controlling rice leaf blight caused by Xanthomonas oryzae pv. oryzae . The fact that bismerthiazol has effect on induction of rice resistance to X . oryzae has been proved. Lipid peroxidation and superoxide anion have increased in the leaves that were treated with the bactericide. O - 2 scavengers, mannotol and ascorbic acid have decreased obviously the protective efficacy of bismerthiazol. Bismerthiazol also has direct effect on inhibiting growth of the bacteria and showed its curative efficacy.