Medial-late Jurassic persilicic volcanic rocks section in Mohe’ertu area, Inner Mongolina, is one of the most important part of Mesozoic volcanic rocks in Da Hinggan Mountains. The zircon U-Pb dating by LA-MC-ICP-MS and SHRIMP techniqu, indicate that the crystallizing age of the volcanic rocks, was from 174.1±2.2Ma to 157.5±2.3Ma, which belongs to medial-late Jurassic. Geochemical researches indicate that the volcanic rocks from Mohe’ertu area are rich in silica (SiO2＝69.12%～80.66%), alkali (K2O＋Na2O=7.26%～8.99%), K (K2O/Na2O＞1.0), poor in calcium (CaO=0.09～0.71), magnesium ( MgO=0.07～0.47，Mg#多＜45) and have high FeOT/MgO (FeOT/MgO=1.50～12.28, average＝4.97) ratio, which is a typical high-K calc-alkaline to shoshonitic series with the character of metaluminous (A/CNK＝1.11～3.07). The rocks are poor in rare earth elements with ∑REE＝95.92×10-6～205.70×10-6 (average＝151.90×10-6), enriched in LREE [(La/Yb) N＝5.17～14.69], LILEs (Rb, Ba, Th, K) and depleted in HFSE, especially Nb, Ta, Sr, P and Ti. The δEu values vary from 0.23 to 0.87 (average＝0.45) and most rocks have moderate negative Eu anomalies. Similar REE distribution pattern imply that the volcanic rocks come from the same magma source. Most of the volcanic rocks with the characteristics of post-collision granites, have lower Sr (Sr=31～187×10-6), high Yb (Yb=1.23×10-6～3.37×10-6, generality＞2) and well geochemical correlation. Combining with previous studies, we suggest that the rhyolitic magma, which has related with Mongolia Okhotsk orogenesis, was formed between late organic and post–collision, that is from 174.1±2.2Ma to 157.5±2.3Ma. The conclusions have most important significance for studying the volcanic action and tectonic settings of medial-late Jurassic volcanic rocks.