Abstract: The mottled structure in the Dabeiwu area can be classified into syngenetic fragments and porphyroblasts, including seven types. On the basis of a study of the distribution and deformation features of the mottled structure, the authors draw the following conclusions: syngenetic fragments are of turbidite origin; syngenetic porphyroblasts are subjected to the control of the ductile shear zone and are one of the important marks of the ductile shear zone in lowgrade metamorphic clastic rocks. According to strain measurements of the mottled structure, the scale of the ductile shear zone is reoutlined and the rate of compression of regional fold deformation and compression amount and shear displacement of the Dabeiwu ductile shear zone are estimated. Finally, the authors point out that there are two stages of deformation for the regional folds and ductile shear in the area.