In this paper, covalently modified graphene (MG) was prepared using graphite and direct ash D as raw materials through diazonium chemistry process to improve its water dispersion properties, so as to suitable for textile industry. The structure, chemical compositions and heat stability of MG were characterized by Raman, Fourier infrared spectroscopy (FTIR), high-resolution X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) etc. The results showed that the dye molecule has been successfully grafted on reduced graphene oxide and the grafting rate reached about 21%. UV-vis spectrophotometer was used to investigate the dispersibility of modified graphene in water and the results disclosed that the dispersibility and stability of MG in water were greatly improved relative to rGO, and the maximum concentration was 0.185mg/mL, and it still remained 0.092mg/mL after 7 days. The modified graphene has both properties of dyes and graphene.