Abstract: A polyether prepolymer was obtained by TDI and PEG, and a polymeric dye monomer was synthesized by linking the Disperse Red R and HEA to polyurethane prepolymer,then a polymeric dye was obtained by monopolymerization.PET fabric was dyed with the polymeric dye and its dyeing behaviour was tested,it was shown that the rubbing fastness and soap-washing fastness are better than those of low-molecular weight dye.