The Gobi, platform, terrace, flat sand land on the edge of the Kumtagh Desert, as well as the interdune and gravel bodies inside the desert are rich in gravel of different sizes. The feathery flowing dune in the central and northern part of the desert core contains more coarse sand, which is rock debris rather than mineral debris. As a temporary intermediate product of weathering of parent rock, lithic fragments are the most reliable and direct indicator of the nature and origin of parent rock. In this study, the coarse grained rock deposits in the Kumtagh Desert were quantitatively analyzed by using the lithology microscopic identification and statistical methods of sand flakes for the first time of the desert research history. The results show that the types of fine gravel and coarse sand rocks in the Kumtagh Desert are very complex, including three rock classes(igneous rock, metamorphic rock and sedimentary rock), 14 rock classes and more than 100 subclasses, which are mainly middle-acid effusive rocks and regional metamorphic rocks. The most common lithologies are rhyolite, felsite, andesite, trachyte, quartzite and quartzitic rock. The lithology of dark particles is mainly middle-acid effusive rocks, while the lithology of light particles is metamorphic rocks and felsic minerals. The quartz fragments have both light and dark colors, which reflects the diversity of genesis and sources. The lithology of the debris is closely related to the grain size of the sand, the grain size of the sand is coarse, the lithology of the rock debris is relatively common with large mineral grains, while the content of the rock debris with fine grain size and the lithology of the parent rock with small mineral grains will increase, and at the same time, the content of single mineral in the sand will increase exponentially. This law makes different regions and different geomorphic locations of the desert, because of the different grain size of the sand. Regional differences of lithology distribution appear. The lithology in the desert is almost exactly the same as the lithology in the Altyn Tagh Mountain. The desert contains not only the common dynamic metamorphic rocks in the Altyn Tagh Mountain, but also various rock types of the ophiolite hybrid series unique to the Hongliugou - Lapaiquan member of the Altyn Tagh Mountain, which fully indicates that the gravel and coarse sand in the Kumtagh Desert come from the weathering of the parent rock of the Altyn Tagh Mountain. The difference of weathering of parent rocks and the different historical stages of mountain uplift make the content of lithology in desert different from that of mountain parent rocks. The cryptocrystalline and fine crystalline rocks resistant to weathering become the main characters of desert sand debris. The granitic rocks and mid-deep metamorphic rocks with coarse grained (crystalline) structure are easier to be decomposed into single minerals and are the main material sources of desert fine sand.