The paleogeography characteristics and water environment of Buha Estuary in Lake Qinghai are similar with those in Or-dos Basin and Sichuan Basin in the Late Triassic.The study on the types of organic matter and its abundance in the surface sedi-ment from Buha Estuary is significant to comparative sedimentology.The sediments were collected from river,prodelta,lakeshore,shallow lake and semi-deep lake in Buha Estuary region and were analyzed in aspects of whole-rock composition analysis,total or-ganic carbon (TOC) and examination of the kerogen.The results demonstrate that Ⅱ₂ kerogen is the major organic matter type in sediments and only a few Ⅱ₁ kerogen exist.TOC content in the sediments is no more than 4.29%,and the samples collected from semi-deep lake generally have high TOC content while the quality of organic matter is better than that of the other places.The clay minerals content in sediments,organic matter productivity and water depth are the major factors that affect the TOC content in the sediments of Buha Estuary.The semi-deep lake is a sedimentary environment which was the most favorable hydrocarbon source place because of its high productivity and good condition for organic matter.At the same time,according to the good correlation be-tween the water depth and TOC contents in sediments gathering from prodelta,shallow lake and semi-deep lake,the formula using the TOC contents has been established for reconstructing water depth.