Abstract: The photoelectric decolorization process of direct orange dye was systematically optimized by single factor experiment and response surface method. The effect of TiO₂ concentration, NaCl concentration, applied voltage, illumination time and other factors on the decolorization effects were discussed. The results showed that under the optimal conditions of TiO₂ concentration of 0.15 g/L and NaCl concentration of 2.85 g/L, the decolorization rate of direct orange solution (pH 7.0) could reach 98.81% while electrolysis at 7.60 V and irradiated for 20 min with 250 W high pressure mercury lamp (main peak wavelength of 365 nm).