Due to the lack of reliable discovery and systematic study of adakitic rocks, it is not clear whether there is an intra oceanic initial arc igneous rock association and intra oceanic subduction in Solonker area, Inner Mongolia, which restricts the further understanding of the Paleozoic subduction extinction process of the eastern part of the paleo Asian Ocean. The study reports that the late Carboniferous adakite in the Suniteyouqi ophiolite, Inner Mongolia, consists mainly of tonalite. The zircon U- Pb LA- ICP- MS dating result reveals that the Chaganbaixing adakite is dated at 322. 3±5. 2 Ma, suggesting that it formed during Late Carboniferous. The adakite belongs to the low- K tholeiitic and medium- K calc- alkaline series. The rocks show following geochemical characteristics, such as high SiO2 (65. 57%~67. 89%) and Al2O3 (15. 48%~16. 55%) content with sodium- rich and potassium- poor (Na2O=4. 13%~6. 33%, K2O=0. 35%~1. 89%, Na2O/K2O=2. 39~18. 09). For trace elements, they show high content of Sr (371×10-6~486×10-6) and low content of Yb (0. 60×10-6~1. 76×10-6) and Y (4. 87×10-6~7. 82×10-6). In addition, they are relatively enriched in large- ion lithophile elements (such as K, Rb, and Sr) and depleted in high- field- strength elements (such as Nb, Ta, Zr, Ti and P). Furthermore, they have low total rare- earth element （REE） contents (22. 83×10-6~80. 63×10-6), with low heavy rare- earth elements（HREE） without obvious Eu anomaly. Above geochemical characteristics indicate that the Chaganbaixing tonalite belongs to adakite. The adakite was formed in the island arc environment of subduction zone, which may have originated from partial melting of the subducted oceanic crust and then interacted with mantle wedge peridotite during the rise of subduction zone. Combined with the study of spatio- temporal evolution of the Chaganbaixing adakite and regional Carboniferous ophiolites, it is assumed that the initial intraoceanic subduction occurred at the Late Carboniferous in the Palaeo- Asian Ocean.