Taking composite insulators with different operation time as samples, the corresponding relationship between temperature T and aging degree of each measuring point is analyzed by infrared temperature measurement, and compared with the characteristic value of the aging degree, transverse relaxation time t2, obtained by NMR test. The results show that T" has obvious linear correlation with t2" after normalization, which can be used as a characteristic quantity to reflect the aging degree of composite insulator. Finally, combined with the water-repellent grade test, the aging grade of the test results was divided, and the parameter estimation method in mathematical statistics was used to calculate the partitioning interval of the aging grade by T" from the sample data, so that the aging degree of composite insulator can be preliminarily evaluated by infrared temperature measurement without power failure.