Abstract: Dry rot is an important postharvest disease of potato tubers caused by Fusarium.This study investigated the effects of chitosan at different concentrations against F.sulphureum and F.sambucinum of dry rot pathogens in potato tubers in vitro and in vivo.Results indicated that chitosan significantly inhibited the spore germination of two pathogens.The rate of spore germination of F. sulphureum was 92% lower than the control, and of F.sambucinum was completely inhibited. Chitosan also inhibited the mycelium growth of two pathogens, the mycelium diameter were 7.46% and 8.9% lower than the control at 0.25% of the optimum treatment concentration.Its inhibition showed more effective to F.sambucinum.Chitosan inhibited the lesion diameter of slices inoculated with F.sulphureum and F.sambucinum, and lesion diameters were 45.3% and 34.5% lower than the control at 0.25% of the optimum treatment concentration. Efficacy was not enhanced when the concentration of chitosan was increased. It is proposed that chitosan treatment could directly inhibit pathogen growth and decrease dry rot of potato tubers by induced resistance.