Infrared thermal wave testing is a non-contact inspection technique that maps the surface temperature of an object after some energy is applied to it. The mechanism of pulsed infrared thermal wave testing was analyzed in detail. Glass fiber reinforced composite was tested by infrared thermal wave testing. Some intensive research on quantitative defect evaluation was developed. Through analysis of the temperature-time curve of two points over a suspected defective location and over a sound area on material surface, the change rule of temperature difference was found. It provided a basis for depth quantitative evaluation. According to the peculiarity of infrared image, an image enhancement approach based on mathematical morphology was adopted, which solve the problem of poor contrast and low signal-to-noise ratio caused by pulse heating. And an image processing program was developed to extract the size information of defects.