Abstract: Through the study of the petrology, chronology and geochemistry of volcanic rocks in Diaoyutai area in Eastern Inner Mongolia, to discuss the formation age of volcanic rocks, the source of magma and the tectonic background in this area, and to provide a basis for studying the magmatic activity and tectonic evolution in the middle part of the Great Xing'an Range during the Mid-Late Jurassic. This paper selects rhyolite tuff from Manketouebo Formation in Diaoyutai area, Studies on petrology, LA-ICP-MS U-Pb dating and rock geochemistry have been carried out systematically. According to the research results, the volcanic rocks of the Manketouebo Formation in the Diaoyutai area of eastern Inner Mongolia were formed in the middle to Late Jurassic (160.3±2.2 Ma), The average SiO₂ content of medium coarse monzogranite is 74.98%, the average Al₂O₃ content is 13.33%, the average CaO content is 13.33%, the average total alkali (ALK) content is 6.96%, it shows high potassium calc-alkaline series rocks. The distribution curve of rare earth elements is right-leaning, with enrichment of light rare earth and deficit of heavy rare earth, significant fractionation of light and light rare earth, and Eu has obvious negative anomaly, the rocks are enriched in Rb、Th、U、Nd (LILE), and depleted in Nb、 Sr、P、Ti (HFS), and the geochemical characteristics are similar to those of A-type granite. Combined with regional geological data and previous research results, the volcanic magma of the Manketouebo Formation in the study area is mainly derived from the partial melting of the crust, which may involve mantle material, and it should be generated in the extensional tectonic background. It is inferred that it is related to the lithosphere extension caused by the plate subduction and retraction after the closure of the Mongolian-Okhotsk Ocean.