The effects of electrolytes on color fastness properties of cotton fabric with Congo Red have been studied at $90^{circ}C$. Each dyeing carried with $10 imes 10^{-6}M$ of Congo Red and with various concentration of electrolytes. The results obtained from this study were as follow 1. In the case of none, the fastness to washing became worse, but the fastness to light better with increasing dye concentration. 2. In the case of additing an electrolyte, the fastness to washing became worse and the fastness to light better than the case of none. The samples had become yellower after washing test. Yellowness had been reduced after fade-O-meter test. 3. What kind of electrolytes could not have any effect on the fastness to washing, but they influenced the fastness to light in the order of LiCl<NaCl<KCl. 4. The higher the electrolyte concentration was, the worse the fastness to washing became, but the better the fastness to light became.