Abstract: Aketenglongshan monzonitic granite is located in the south margin of South Altyn. Here we present whole-rock geochemistry, zircon U-Pb geochronology and Hf isotope analysis to study the petrogenesis and magmatic evolution of the granite, which belong to high-K calc-alkaline, weakly peraluminous series and I-type granite. The geochemical characteristics show strongly fractionation of the REEs, and enrichment in LREE, while depletion in HREE. It is infered that amphibole, apatite and rutile fractionation occurred during the magmatic evolution. The zircon U-Pb age of the granite is 435–449 Ma, representing the crystallization age of the granite. The half negative and half positive value of zircon ε_Hf(t) indicates that the origin of the monzonitic granite is mixture of juvenile and ancient crust materials, and the granites were derived from the partially melted juvenile crust, and mixed with ancient crust materials during the upwelling, or derived from the partially melted mixture of juvenile and ancient crust materials, in extensional environment transformed from compressional environment after the break off of the subducted oceanic crust.