Abstract: Composite insulators can be affected by the external environment in the process of operation,and will have different degrees of aging.In order to explore the aging characteristics of composite insulator sheds after operation,5 samples of composite insulator sheds after operation were selected for hardness test,Fourier infrared spectrum detection and thermogravimetric infrared combined test.The results show that the aging degree of the surface layer of the same sheds is more serious than that of the inner layer,and the aging of the sheds running on the same insulator with high electric field intensity is more serious.The types of gas phase products generated by the TGIR test between the aged sheds and the non-aged sheds is unchanged,but the generation of CH₄ gas phase products decreased.