The SF6/N2 gas mixture, as an alternative to SF6 in gas-insulated systems within the power industry, has gained significant attention and application. However, the effect of trace amounts of moisture on its decomposition characteristics remains unclear. To further investigate the feasibility of replacing SF6 with SF6/N2, this study employs molecular dynamics simulations to explore the decomposition mechanism of a 30% SF6/70% N2 mixture in the presence of trace moisture at the microscopic level. H2O molecules introduce hydrogen radicals, which attract F radicals, thus influencing the decomposition process of the SF6/N2 mixture. As the moisture content increases, the number of hydrogen radicals rises, leading to an increase in SF6 decomposition. In contrast, N2 decomposition fluctuates but is eventually suppressed as the amount of H2O molecules grows. The decomposition products of the SF6/N2 mixture tend to form stable structures such as SF2, SF4, and NF3, with SF2 and SF4 easily reacting further to generate SOF2. The formation of SOF2 in the equipment can reduce insulation performance, and the simultaneous production of HF, a highly corrosive substance, degrades the performance of gas-insulated devices. Therefore, measures should be taken to monitor its concentration. This research provides theoretical support and engineering guidance for understanding the decomposition mechanism of the SF6/N2 mixture under trace moisture conditions.