The Haorigeshan pluton in Inner Mongolia is located at the junction between the northern margin of the North China and southern margin of the Central Asian Orogenic Belt. A systematic geochemical study can facilitate understanding the tectonic- magmatic evolution and geodynamics background of the belt from Late Paleozoic to Early Mesozoic. The Haorigeshan pluton consists mainly of monzogranite, which can be further divided into muscovitebiotite monzogranite and porphyritic biotite monzogranite. Zircon UPb dating yields weighted 206Pb/238U ages of 244.9±1.6 Ma and 230.2±1.5 Ma for them respectively, indicating that the Haorigeshan monzogranite formed in the EarlyMiddle Triassic. Geochemical results show that the Haorigeshan monzogranite has SiO2 of 72.58%~74.42%, K2O of 4.06%~5.82%, Na2O of 3.08%~3.88%, Al2O3 of 13.39%~14.55%, and A/CNK of 1.02~1.13, suggesting high- K calc- alkaline and peraluminous. Relatively low total REE, enrichment of LREE relative to HREE, negative Eu anomalies, high contents of Rb, U, Hf and low contents of Ba, Nb, Ta, Ti and Zr, all suggest that the Haorigeshan monzogranite is characteristic of high fractionated granite. Zircon Hf isotopic analysis displays that εHf(t) values are nearly negative and consistent with that Triassic granites in the northern margin of North China Craton, suggesting that the source region of Haorigeshan monzogranite is more close to the North China Craton. This study shows that the Haorigeshan monzogranite formed in the post- collision tectonic setting, which is closely related to the final closure of paleo- Asian ocean.