Abstract: The blast furnace slag was modified with DTAC to prepare a low-cost and environment-friendly adsorbent for the treatment of dye wastewater. The study analyzes theadsorbent dose, adsorption time, initial dye concentration and pH value on the adsorption capacity of KN-R reactive brilliant blue from the modified slag , and the variation rule of characterization of the modified slag was also analyzed. The results show that when the amount of modified slag is 10 g/L, the initial concentration of dye is 60 mg/L, the pH value is 2, and the adsorption time is 120 min, the maximum decolorization rate of the modified slag can reach 96%, and the initial concentration of 150 mg/L is the optimal solubility, the decolorization rate and adsorption capacity are both high at this concentration. Through XRD and FTIR tests, the characterization characteristics of slag and modified slag were compared and analyzed. It was found that DTAC could better modify slag, and the adsorption capacity of modified slag was significantly improved.