Abstract: On the basis of the analysis, identification and estimation of the clay minerals of northern Jiangsu, this paper deals with a more detailed analysis of the charac-teristics of the contents and combinations of the clay minerals.According to the morphology of thereflecting peaks of the X-ray diffraction spectrum pattern of the clay minerals,the difference in intensity and the distribution of the peak heights at 7Ä，10Ä and 14Ä in the triangular diagram, the surficial clay minerals in that region may be subdivided into three regions, namely: the region of the underwater delta of the ancient H uanghe River(I)，the radial sand bar region(II)，and the region of the north side of the Changjiang River mouth(III).In constrast with the clay mineral characteristics of the coastal land and rivers，it is found that the sediments of region(I)were mainly affected by the ancient H uanghe River, those of region(III) mainly came from the Changjiang River,and those of region(II)were a mixture of the sediments of the ancient H uanghe River and the C hangjiang River in its early stage.According to the analysis of the correlation data on grain size, heavy minerals,chemistry, spores and pollen, and ancient microorganisms, the distributional charac-teristics of the clay minerals have been further verified and supplemented.After the contrast is made between the distributional characteristics of the clay minerals and the data on suspended substances,salinity，hydrodynamics and sub-marine relief, it has been shown that the movement and spreading conditions of the sediments of this region are controlled by the hydrodynamic conditions.This has been also verified by satellite images.T hus,the clay mineral characteristics play an important role in the study of the sedimentary features.