Abstract: The effect of citric acid at different concentrations against Fusarium sulphureum and F.sambucinum of dry rot pathogens in potato tubers was studied in this paper.Results indicated that citric acid inhibited significantly the mycelium growth and spore germination of F.sulphureum and F.sambucinum, and its inhibition efficacy was greatly enhanced when the concentration of citric acid was increased, the mycelium diameter were 28.83% and 21.59% lower than the control after treatment with 2% citric acid, the spore germination of F.sulphureum were 94.02% lower than the control, completely inhibited the spore germination of F.sambucinum.Lesion diameter of slices inoculated with F.sulphureum and F.sambucinum were decreased by citric acid treatment when concentration at 0.5% showed the most effective, the lesion diameter reduced by 59.01% and 55.02% compared with the control.A higher concentration treatment did not increase the effect.It was suggested that citric acid treatment could directly inhibit pathogens and induce resistance to decrease dry rot of potato tubers.