Responses of permeability in six wheat varieties to Fusarium graminearum crude toxin were studied under different stress time and different toxin concentration. The results showed that root cell membranes were all susceptible in 72 hours' toxin stress. Relative electric conductivity increased with the increasing of toxin concentration and the elongation of toxin stress time. Resistant varieties had stronger resistance to toxin stress than susceptible varieties and increment of relative electric conductivity were lowest. The increment of membrane permeability was all highest after 72 hours' stress and showed significant difference. Then the increment of membrane permeability of resistant varieties decreased.