Abstract: The changes of polyamines and the indole acetic acid metabolism of sweet potato cultivars with different resistance to sweet potato scab before and afterinoculation were studied.The results show that the indole acetic acid content and the polyamine oxidase activity decrease,the total content of polyamines and putrescine increase,the ratio of putre-scine/ (spermidine+spermine)increases in the leaves of both resistant and susceptible sweet potato after infected with scab fungus.But the change range of diseased sweet potato is more extensive than that of anti-diseased one.The chlorogenic acid content decreases,the indole acetic acid oxidase and peroxidase activity increase in the leaves of susceptible sweet potato after infected with scab fungus,and the change of resistant sweet potato is contrary.