Okinawa Trough is tectonically a back-arc basin of a trercharc-basic. sys- tem. The unceasing extension of the basin has caused intensive and repeated vol- caztic activities in the bottom of the trough. During the volcanic activi+ies of the latest stage large amounts of intermediate or acid pumice were formed., which constitute the main submarine rocks emerged from the bottom of the 1rough. The pumice in Okinawa Trough is distrzbuted in a NE-SW direction and in an intermittent linear way, which is closely related with the submarine mountains, The pumice encountered on the bottom of the through represents the cognate and isogenetic volcanic eruptive material, i. e.，the liparite-pumice that is intermediate and acid yet meta-acid in acidity and belongs under the calc-alkaline series,The submarine eruption is of effusivetype. The pumice is with typical pumrceous structure and porphyritic texture, The pher,ocryst is usually high,-temperature andesine or hypersthene and occasionally quartz. It is character istic of the phenocryst containing relatively more vitric as well as monocyclic and binary enclosures of vitric and gas, The ground mass is acid volcanic glass (N=1.496-1.500).There is a lot of CO2 in the bubbles, The temperature for crystallization of the phenocryst of high-tempera+ure andesire is 1050-1100℃. The pumice contains fine debris enclosures of basalt and andesite, ia:dicating it represents the eruptive material following basal1 and andesite, Judged from the rocks,the pumice falls in the followitug rock assemblages tholeiite, andesite-, liparite-andesite-pumice and liparihe-pumice. The age of the pumice determined by the method of thermoluminescence is 35400-37100yers, which shows the pumice was formed in the late pleistocene. The pu-mice is arc-volcanic rock.