Late Precambrian mafic dyke swarms are extensively developed in the central North China Craton. These dyke swarms are undeformed and unmetamophosed with beautifull flow structure to show the characteristics of Precambrian magma activity, which is rare in the world. The direction and way of the dyke emplacement are proposed based on the study of the shape and flow structures of Late Precambrian mafic dyke swarms; for example, flow lineation, mineral fabric and magnetic fabric. The origin of dyke emplacement is discussed according to the relation between the dykes and the Yanliao-Zhongtiao aulacogens as well as the mechanics of the dykes.