In dyebath of acid and cationic dye solution, the effects of pH, dye concentration and dyeing temperature on dyeing properties were investigated by the measurement of the interfacial electrokinetic potential of wool and acrylic fiber. The interfacial electrokinetic potentials were measured by streaming potential method which was generally used in the electrochemical study of interface of fiber and dye solution. The results were transformed into potential by Helmholtz-Smoluchowski formular, into surface charge density by Suzawa formular and into surface dye adsorption of fibers. The f potential of wool in dyebath of acid dye was decreased by the formation of ionic bonding between positively charged wool and acid dye. The f potential of acrylic fiber in dyebath of cationic dye was increased by the formation of ionic bonding between negatively charged acrylic fiber and cationic dye.