Abstract: Studies on the Paleozoic tectonic evolution of the East Kunlun Orogenic Belt are of great significance for understanding the tectonic framework of the Tethyan realm. This study systematically investigated petrology, petrogeochemistry, zircon U−Pb geochronology, and Hf isotopes of the monzogranite from the Walega South Gold Deposit in the Gouli Area, East Kunlun Orogenic Belt. This research aimed to determine its emplacement age and tectonic setting, thereby providing new insights into the geological evolution of the eastern segment of the East Kunlun Orogenic Belt during the early Late Paleozoic. Zircon U−Pb dating yields a crystallization age of 410 Ma±7 Ma for the monzogranite, indicating the occurrence of magmatic activity along the northeastern margin of the East Kunlun Orogenic Belt during the Early Devonian. Petrogeochemical results show that the monzogranite is characterized by high content of SiO₂, Al₂O₃, and alkali, and belongs to strongly peraluminous S-type granite. It is relatively enriched in large-ion lithophile elements （e.g., Rb, U, and Pb） and depleted in high-field-strength elements （e.g., Nb and Zr）, exhibits weak fractionation between light and heavy rare earth elements, and displays pronounced negative Eu and Ce anomalies. Combined with zircon ε_Hf（t） values ranging from −12.9 to 2.3 and corresponding two-stage Hf model ages （1.24–2.20 Ga）, these findings indicate that the monzogranite was generated by a high degree （75%–85%） of partial melting of Paleoproterozoic metagreywacke in the thickened lower crust. Tectonic discrimination suggests that the monzogranite formed in a post-collisional extensional setting. This reflects the transition from crustal thickening to thinning in the East Kunlun Orogenic Belt during the Early Devonian, corresponding to the post-collisional extensional stage following the closure of the Proto-Tethys Ocean. These results provide crucial geochronological constraints for refining the early Paleozoic tectonic-magmatic evolutionary sequence of the East Kunlun Orogenic Belt.