The invention discloses a method and a system for detecting pollution grade of a composite insulator based on high spectrum. The method comprises the following steps: firstly, obtaining a high spectrum image of the insulator with unknown pollution grade; treating the high spectrum image of the insulator with unknown pollution grade by a pollution grade model, and judging the pollution grade, wherein the pollution grade model is established according to the feature wavelengths in pollution images of the insulators with different pollution grades. The method has the advantages that a high spectrum imager is used for non-contact detection, the operation is convenient and rapid, and the method is suitable for live detection at site; the pollution grade can be identified from the high spectrumimage information, the pole climbing for detachment of the insulator is not needed, the shutdown of the line is not needed, the foundation is provided for the targeted and pertinent cleaning of the insulator, and the national requirement on detection of the insulator of a power transmission line is met.