Abstract: With glass fiber composite material as the research object, the regularity of frequency variation of acoustic emission wave in glass reinforced plastics was studied, and it was found that acoustic emission wave attenuation frequencies collected from different locations of the acoustic emission sources were concentrated in different areas. According to the theory of modal acoustic emission that acoustic emission signal propagation characteristics are different in different frequency ranges, acoustic emission wave was filtered by different passband filters, and the linear relationship about its time difference to each sensor were analyzed for the purpose of comparison, and hence a precise method of extracting the acoustic emission wave arrival time was obtained and it was found that the error of the mode filtering was significantly lower than the traditional time.