Abstract: On the basis of a study of ductile shear zones in granitic rocks in an Early Precambrian metamorphic terrain of Shanxi province the author preliminarily summarizes the features of narrowing and widening ductile shear zones. It is considered that migmatization is ″,self-dif-ferentiation″ causing rocks of widening ductile shear zones to occur under the effect of exten-sional structure.