Abstract: I/S clayrock bands and beds of Carboniferous-Permian Coal-bearing Formation in Northern China have wider distribution in the eastern Taihang Mountain. The types of I/S interstratified mineral have rectorite, ordered IS and disordered S/I. They were formed by the synsedimentary fallout-ash alteration in the nearshore peat swamp and march environment. The ordered IS minerals were formed in acidity medium; the disordered S/I minerals formed in the alkaline one, and the rectorite was formed in the abnormal regions of high pressure.