The invention discloses a spectral measurement method for the transformer insulation paper polymerization degree. The method comprises the steps of building a mathematic model for insulation paper polymerization degrees on the basis of the polymerization degree of the standard insulation paper patterns, the wavelengths of irradiation light waves and the diffusion reflection light intensity; during field using, measuring the corresponding light intensity of the diffusion reflection of the light wave, passing through the surface of an insulation paper pattern with the to-be-measured polymerization degree, of the corresponding wavelength through a spectral measurement device, and inputting the wavelength of the irradiation light waves and the light intensity of the diffusion reflection into the mathematic model for the insulation paper polymerization degrees to obtain the polymerization degree of the insulation paper pattern with the to-be-measured polymerization degree. After the mathematic model is built on the basis of the diffusion reflection light intensity of the standard insulation paper of different polymerization degrees for light of different wavelengths, during field transformer insulation paper detection, the polymerization degree of the field transformer insulation paper can be obtained only by utilizing the corresponding spectral measurement device for measuring the diffusion reflection light intensity of light of different wavelengths and inputting the light intensity into the mathematic model. The measurement method and device are quite simple and rapid, and no damage will be caused to the transformer.