As one of the Holy Grail reactions in C1 chemistry, direct selective oxidation of methane to methanol under mild and non-harsh conditions remains a big challenge. Hydroperoxide (H₂O₂), as a primary oxidant, applied widely in the lowtemperature direct selective conversion of methane to methanol. Moreover, the hydrogen and oxygen mixture gas achieves better reaction activity and higher methanol selectivity than H₂O₂ when using palladium-gold (Pd-Au) bimetallic nanoparticles as the catalyst. In this paper, we studied the key roles of the physical and chemical characteristics of Pd-Au nanoparticles in this direct selective oxidation reaction with hydrogen and oxygen as the oxidant at 50°C. For further clarifying the physical and chemical characteristics of catalysts, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Hydrogen-Temperature-programmed reduction (H2-TPR), and CO pulse adsorption measurement (CO-PULSE) analysis methods are also measured.