The tuber roots of susceptible sweet potato were injected with exudate from D. destructor. The tissue aroud inoculated holes about 1~1.5cm became brown and light rot. The hole walles of resistant variety were brown only by same method, The cells of brown tissues of suscebtible variety were booken down and disrupted;parenchyma cells of hole wall of resistant variety were induced to produce cork layer. The responses were the same as those inoculated with the nematode suspension. The section of sweet potato of resistant and susceptible varieties were added quantitatively with exudate of D. destructor. Resistant callus was stimulated to form giant gall and tissue hyperplasia. There was no such phenomenon in susceptible callus and contrast. Parenchyma cells of gall were three and four times larger than normal cells. There were few starch particles and crystals in the cells of gall. But the cell walls were not collapse The cells of surface layer of gall were stimulateb to form cork layer after treated for 30 days. Analysis of the exudate by soldium dodecyl sulfate-polyacy-rylamied gel electrophoresis revealed the presence of eighteen protein bands with silver strain. Based upon the molecular weights of commercial standards, the proteins in exudate ranged from 16k to 93k daltons.