The Guoluolongwa gold deposit, located in the Gouli district of the Eastern Kunlun Orogenic Belt, exemplifies a Late Devonian-Early Carboniferous post?collisional extensional magmatic?hydrothermal vein?type gold system. We employed comprehensive field mapping, backscattered electron imaging (BSE), TESCAN mineral analysis (TIMA), in situ LA?ICP?MS trace element profiling, and LA?MC?ICP?MS sulfur isotope microanalysis to unravel its ore genesis. Four paragenetic stages were delineated—Stage I (quartz-pyrite), Stage II (quartz-arsenopyrite–pyrite), Stage III (quartz-polymetallic sulfides), and Stage IV (calcite-quartz)—and three pyrite generations (Py1-Py3) were identified. Progressive variations in trace element concentrations (Co, Ni, As, Au) and Co/Ni ratios among pyrite generations confirm a dominantly magmatic?hydrothermal fluid source. Pyrite δ34S values decline from 3.77‰ to 5.95‰ in Py1 to -2.60‰ to 0.06‰ in Py3, reflecting incremental oxidation and meteoric water infiltration that lowered H?S activity and drove sequential sulfide and gold precipitation. Integrating Re-Os ages (375~354 Ma) and Pb-H-O isotopic data, we propose a genetic model whereby magmatic?hydrothermal fluids migrated along EW?trending faults and precipitated in structural conduits during post?collisional extension.