The invention discloses a piece goods blemish detecting method based on morphological analysis. The piece goods blemish detecting method comprises the steps that a line-scan digital camera is used for conducting image collection on piece goods in motion, the distance of adjacent tissue points of the piece goods is obtained by conducting basic brightness stretching and binaryzation processing on gray level images of the piece goods, and the distance serves as the reference value of the size of structural elements; then, morphological close operation is conducted, filling is conducted on common weaving point gaps, the number of the weaving points at a blemish position is small and the weaving points at the blemish position are irregular, so that the weaving points stand out in brightness; at least, binaryzation processing is conducted on the images, determining of the threshold of the images is controlled through gamma training selecting of gray level power transform, blemished binary images are counted and marked, blemish information is output, and the blemish detecting process of the piece goods is completed. The piece goods blemish detecting method based on morphological analysis is more accurate and simpler in structure, and improves the calculation speed; can weaken the interference of background brightness unevenness; brings convenience to realization of automatic detection.