In order to study the dyeability of wool, S-cyano ethylated wool-keratine(SCEK) as a model compound of wool was prepared from the reaction of reduced Merino wool fiber and acrylonitrile. It was found that the cyano etylation modified the $alpha$-helix structure of microfibril. The binding ability of acid dyes (methyl orange and its homologs) to SCEK and the permeation properties of SCEK membrane were investigated. The first binding constants and the thermodynamic parameters in the course of binding were calculated from the binding experiments with methyl orange in the temperature range of 30-50 ˚C. The free energy change was accompanied by exothermic enthalpy change and entropy gain. These characteristics of thermodynamic parameters suggest that hydrophobic interaction plays a role in the binding of SCEK. The binding ability of ethyl orange and butyl orange showed a cooperative binding phenomena, especially in concentrated solutions. In relation to hydrophobic interaction, the effects of urea were examined. The amounts of bound dye were decreased with the addition of urea in solution. For wool, the bound dye was stacked at concentrated solutions. The permeation coefficients of SCEK membrane were in the order of 10 9 - 10 8 mol/min. in the temperature range of 30~50˚C. The smaller the size of dye molecules, the better the permeability of SCEK membrane was.