This paper provided petrography, geochemical characteristics, LA- ICP- MS zircon U- Pb age of Adelaga alkali feldspar granite, in Abaga Banner, Inner Mongolia. The formation age, genesis and tectonic significance of granits are discussed.Methods:Based on the field work, through the microscopic observation, the whole rock chemical analysis, the LA- ICP- MS zircon U- Pb isotopic chronology of granites.Results:The Zircon LA- ICP- MS U- Pb ages indicates that the Adelaga alkali feldspar granite is 310.7±2.6Ma, and formed in Upper Carboniferous. The granite has the character of Higher content of SiO2, Na2O+K2O, higher ratio of Ga/Al,（Na2O+K2O）/CaO, and relatively poor CaO, MgO, Sr, Ba, Eu, Ti and P. The total amount of rare earth elements is low, the fractionatio of light and heavy rare elementsis not aobious, the distribution curve of rare eatrh is seagull, and the anomaly of negative europium is obvious (δEu=0.15~0.37). The granite belong to A- type granite. Conclusions:The Adelaga alkali feldspar granite is A- type granite, and formed in back- arc extensional tectonic setting of Upper Carboniferous, which is the product of Paleo- Asian Oceanic subduction to Siberia.