Abstract: In this paper, the defects in three types of composite insulators, namely, core sheath air gap defect, core internal air gap defect and process iron chip internal residual defect, were fabricated manually in the laboratory. High voltage test platform and conduct test. Obtain infrared image of composite insulator using infrared detection equipment. The research shows that the temperature rise of three artificial defect insulators exists. The temperature rise of residual defects in process iron filings reaches 4.5 K, and the heating area extends from near the fittings to two umbrella skirts. When the humidity increases by about 35%, the temperature rise amplitude of the internal defects of the mandrel increases by 73.67%. The research results can provide reference for infrared detection of internal defects of composite insulators on site.