The dyeing property of milling type acid dyes with various chemical constitution were studied in one bath dyeing of Wool/Nylon blended fabrics and the proper dyeing condition to get solid color by using reserving agent was also examined. The result of the experiments can be summarized as follows; 1) Although the effect of pH on dyeing of wool with a highly hydrophiilic dye is great in the dyeing of wool and nylon, the proper pH of dyeing bath is weakly acidic 5, in which levelling dye can be obtained by increasing the solubility product. 2) Under a constant pH, the dye with fewer numbers of sulfonic acid groups increases the dyeing amount of nylon as the concentration of the dye is increased. Thus the appropriate dye for light color is the one with many numbers of sulfonic acid groups and the proper dye for medium and deep color is of fewer sulfonic acid groups for one-bath dyeing. 3) When the dye concentration is greater than the critical depth, the K/S value of wool and nylon was almost not effected or slightly increased.