The invention relates to a composite insulator aging state evaluating method. The method comprises the steps of (1) implementing accelerated aging according to an IEC62217-2005 standard; (2) regularly carrying out infrared spectral analysis, (3) drawing relation curves of the peak areas corresponding to a Si-O-Si main chain group and a Si-CH3 side chain group and the revolution of accelerated aging, (4) the more obvious the descending trend of the two relation curves is, the weaker the anti-aging ability of a composite insulator is, and the deeper the aging degree is, the anti-aging ability of a composite insulator with a segmented phenomenon is better than that of a composite insulator without a segmented phenomenon in the descending process of the two relation curves. According to the method, the aging state of the composite insulator can be evaluated according to the result of the infrared spectrum analysis, an insulator with a high aging degree is replaced in advance, the transmission line trip caused by the failure of the composite insulator is prevented, and the safe and reliable operation of a power grid is ensured.