A modified dicyandiamide?formaldehyde decolorizing flocculant was prepared using cyclohexylamine as modifier, and was used to simulate dye wastewater decolorization, flocculation and sedimentation experiments. The effect of reaction temperature, reaction time, material molar ratio and other factors on the decolorization performance of the modified flocculation was studied. The results show that reaction time is 3.5 h, reaction temperature is 85 ℃, material molar ratio of dicyandiamide to formaldehyde to ammonium chloride to cyclohexylamine is 1.00∶3.00∶0.50∶0.15, the decolorization rate 88.6% is achieved at a modified flocculant dosage of 100 mg/L. The decolorization and flocculation performance of the dicyandiamide?formaldehyde modified decolorizer is obviously better than that of the unmodified product.