Results of research on the petrological, petrochemical, rare elements′and trace elements′character-istics of the volcanic event layers in Mid-Taiyuan Formation from middle region of Shanxi and western region of Hebei are presented. Petro-geochemical features, REE distributions, seven-even-numbered- el-ement curves of REE and ratio spiderg rams of trace elements for these pyroclastic rocks perfectly resem-ble, and according to the application of the theory of power function, these pyroclastic rocks considered here should belong to the isochronal products of the same resource, coming from the calc-alk volcanic eruption in island-arc part. The discovery of the isochronal pyroclastic rocks provide the significant in-formation for the division and correlation of strata. In this paper, we can take these volcanic event layers as a marker bed to make regional strata correlation in this area.