Abstract: In this paper, the types, composition, distribution and origin of the main clay minerals of sadiments in the middle of the Pleific Oeean are initially analysed and studied, -which offers an important insight into the understanding of the sediments in respect to their origin, transport, environment and history. The clay minerals are mainly dioctahedral Fe-Al montmorillonite characterized by its broad crystalliaityj trioctahedral Fe-Mg chlorite,some of which are good in their crystallinity, but some poor; dioctahedral Fe-Al hydromica ( illite ) of muscovite type, having the stable properties of crystallo-chemistrys kaolinite with a property of chanegeable order,including the highly-ordered and double-layer dickite and poorly-ordered kaolinite as well as some mixed-layer ones, such as illite-montmoril-lonite, illite-chlorite and kaolinite-montmorillonite and palygorskite in small amount. Among clay minerals, the montmorillonite and chlorite are mainly authigenic, and the muscovite and kaolinite are mainly terrigenous origin from Australia. During the chilly glacial epoch, the sea level fell and the tein perature of the sea water reduced.Meanwhile the dissolution of the carbonate decreased, and the carbonate in the sediments was rich, while the total amount of the clay minerals was poor. In addition,the volcanic activites were quite violent and the sources of the basic volca-aic material were abundant, Therefore, the relative amount of the authigenic montmorillonite was bigger than that of the other clay minerals, and the ratio of montmorillonite to illite was relatively bigger. The situation of the interglacial anci the post-glacial ages was contrary to that of the glacial age.