Abstract: The identification method of PLA and PET fibers was explored.The findings showed that the PET fiber has a more compact structure than that of PLA fiber,and the holes or cracks on the cross sections of PLA fiber may be observed under microscope.In addition,there are obvious differences between FTIR spectrums of the two fibers.In the case of fiber DSC performance,the melt and apex temperatures of PET fibers are 90 ℃ and 84 ℃ higher than those of PLA fiber respectively. The alkali solution(pH value=11.8) will damage PLA fiber significantly,but almost no impact on the strength of PET fiber,and this can be also used as a qualitative identification of the two fibers.