Abstract: Multi-walled carbon nanotubes (MWCNTs) were modified by grafting an amphiphilic polymer, which were characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The modified MWCNTs were added to an intumescent fire-retardant coating and their effects on the performance of the coating were studied. Results show that the amphiphilic polymer can be attached to the surface of MWCNTs by appropriate processing, and the modified MWCNTs exhibit a remarkable solubility in butyl acetate and distilled water. The modified MWCNTs added to the coating can strengthen the carbonized layers, increase intumescent times and decrease the increasing rate of the rear temperature when the coating was exposed to a fire. The modified MWCNTs can also enhance the crack resistance of the coating.