Abstract: The Huangtuyao crystalline graphite deposit in Xinghe, one of the key crystalline graphite deposits in China, is located at the northwestern margin of North China Craton. The deposit occurs in the lower segment of Huangtuyao Formation. Through the field survey and microscopic mineralogical study combining with geochemical analysis, the ore bodies are hosted by graphite-bearing plagioclase leptynite, subordinately graphite-bearing diopside-tremolite leptynite. The average fixed carbon grade of the ore bodies is 5.31 %. The ore minerals are in the form of flakes with 89 % of big flake graphite (>0.15 mm or 100 mesh size) and 11 % of small to middle flakes (<0.15 mm or 100 mesh). The diagram of w(Zr)/w(TiO₂)-w(Ni) and the diagram of (al+fm)-(c+alk)-Si show that the original rock of the metamorphic rock is clay-rich sedimentary rock, the diagram of KA, the diagram of Ba-Sr and the w(La)/w(Yb)-w(REE) diagram show that the ore was formed in a semi-saline calcareous mudstone depositional environment. The average value of the δ¹³C test of the graphite mine is -22.35 ‰, indicating that the carbon source of the graphite is organic carbon. The formation of the graphite deposit in the Huangtuyao area is inferred to be in a shallow marine-coastal facies of muddy fine-grained sandstone with strong biological activity. The ancient marine environment with rich organic matter provides the carbon source for the formation of graphite deposits, and then undergoes metamorphism to form crystalline large scale graphite deposits. This feature can be used as a geochemical criterion for the exploration of graphite deposits in the same layer. Therefore, Huangtuyao is a sedimentary-metamorphic crystalline graphite deposit of organic carbon origin.