Abstract: Pseudomonas solanacearum is a major diseases in sweet potato which leads to substantive yield loss and quality degradation. Changes in phenylaprapanoid metabolism were studied in resistant and susceptible cultivars of sweet potato seedlings after inoculation by leaf-cut. The results indicate that PAL and POD activities in resistant and susceptible cultivars increase after inoculation. However, the rates of increase in PAL and POD activities are directly related with cultivar resistance to pathogens. Lignin and chlorogenic acid contents increase significantly after inoculation of resistant cultivars. Though chlorogenic acid, total phenolics and flavonoids contents largely fluctuate after inoculation, and lignin content decreases in susceptible cultivars. The relative analysis shows that the accumulation of lignin and chlorogenic acid has close correlation with cultivar resistance. Rapidly increase in PAL and POD activity and in the accumulation of lignin and chlorogenic acid after inoculation is the basis for phenylaprapanoid metabolism against P. solanacearum in sweet potato. This can find application in referencing resistant cultivar identification.