The invention discloses a method and a system for detecting bonding defects inside a composite insulator. The method comprises the following steps of acquiring a visible light image, a first speckle image and a second speckle image of a detected composite insulator through laser array equipment, thermal excitation light source equipment, and imaging equipment; performing operation processing on the first speckle image and the second speckle image through the data processing equipment to obtain an interference fringe image and a phase image; and performing Gaussian filtering processing, drawingan edge image to integrate with the visible light image to obtain an integrated image, and identifying bonding defects inside the composite insulator. Through the method disclosed by the invention, the rapid, accurate, non-contact and visual detection of the bonding defects inside the composite insulator is realized, the defection effect on the tiny bonding defects inside the composite insulatoris good, an aim of efficiently and accurately detecting the bonding defects inside the composite insulator is realized; and the method is simple in operation, visual in imaging, the influence by the operation subjective factor of a detector is small, and the objectivity and the scientificity of the detection can be effectively guaranteed.