Abstract: In recent years, Late Mesozoic porphyry-type molybdenum deposits in the Northern Greater Khingan Mountains have gradually attracted attention and been reported. However, due to limited exploration in certain mining areas, studies on the sources and evolution of ore-forming fluids, as well as the origins of ore-forming materials for these deposits, remain insufficient, leaving many geological questions unresolved. This study selected the 770 Molybdenum （Copper） Deposit as the research subject, conducting sulfur and lead isotope analyses on metal sulfides from ore samples of the main mineralization stage, and hydrogen and oxygen isotope analyses on quartz from ore samples, to reveal the sources of ore-forming fluids and ore-forming materials. The orebodies of the 770 Molybdenum （Copper） Deposit occur within Late Jurassic granite porphyry, which is closely associated with mineralization. The sulfur isotope compositions of metal sulfides exhibit small positive values, ranging from 0.33 ‰ to 1.41 ‰, indicating a homogeneous source of ore-forming materials likely derived entirely from magma, specifically the Late Jurassic granite porphyry. Lead isotope tectonic model diagram of metal sulfides show data points primarily plotting between the crustal and mantle evolution lines, suggesting a mixed crust-mantle origin for the lead isotopes. Hydrogen and oxygen isotope analyses of quartz reveal that Stage Ⅱ quartz has δ¹⁸\mathrmO_\mathrmH_2O values of 4.7 ‰, close to those of primary magmatic water, implying that the ore-forming fluid during this stage was predominantly magmatic. The δD value of −121.0 ‰ in Stage Ⅱ is significantly lower than typical primary magmatic water values, potentially linked to magmatic degassing or water-rock interactions. For Stage Ⅲ quartz, δ¹⁸\mathrmO_\mathrmH_2O values range from 0.6 ‰ to 2.3 ‰, with δD values between −132.9 ‰ and −130.9 ‰, falling between primary magmatic water and meteoric water fields but closer to the magmatic water domain. This suggests that while meteoric water was introduced during Stage Ⅲ, magmatic water remained dominant, indicating a mixed fluid source of magmatic water and meteoric water during mineralization.