The work aims to explore the relevant characteristics of resistance to black rot by studying the cell wall changes of sweet potatoes with different black spot resistance. Fresh sweet potato varieties 'Xinxiang' and 'Yanshu 25' with different resistance were used as test materials. The resistance characteristics of the two varieties to black rot were analyzed by inoculating the Ceratocystis fimbriata culture method. The possible mechanism of resistance was analyzed by determining relevant indexes of the cell wall during storage. After inoculation with Ceratocystis fimbriata, the surface diameter, internal diameter, comprehensive diameter, depth, and decay index of 'Yanshu 25' with black rot were less than those of 'Xinxiang', and its comprehensive resistance was better. The diseased region of infected sweet potato showed a gradual decrease in hardness and protopectin content, a gradual increase in soluble pectin and lignin content, a first increase and then a decrease in cellulose content, a first decrease and then an increase in cellulase, and a gradual increase in β-glucosidase content. Hardness, soluble pectin, cellulose, lignin content and β-Glucosidase activity of diseased tissue of 'Yanshu 25' were significantly higher than those of 'Xinxiang'. While its content of protopectin and cellulase activity decreased significantly. The difference between these two varieties was greater after infection. The infection of sweet potato by Ceratocystis fimbriata will lead to the decrease of hardness and the disintegration of the cell wall structure. The resistance of 'Yanshu 25' to black spot was better than that of 'Xinxiang'. Its cell wall structure is more integrated, and the hardness is higher.