Abstract: Diatom plays a significant role in the carbon cycle of the whole world.Thriving to mats in the subsuface water, the "shade flora" is buried rapidly and becomes diatom mat deposits.The subsuface diatom production plays a considerable role in the whole productivity and output productivity. The distribution of diatom mat deposits discovered in the west low-latitude Pacific Ocean is introduced in this paper. Diatom mats are in banded distribution,spreading in NW-SE direction and most distributed in deep water areas, between 17.5°~20° N and with water depth of 4 837~6 150 m below CCD,where strong wind and land material input occur. The formation of diatom mats in this area may be due to the formation of ocean front in the last glacial period. The diatom Ethmodiscus rex(Wallich)Hendey in this area is a typical "shade flora" diatom, which can live and thrive in the oligotrophic open ocean by their regulating and floatation abilities. The occurrence of diatom mat deposits in the west low-latitude Pacific Ocean in the last glacial period makes this area become the sink of CO₂ probably.