FTIR, XRD, Raman, AFM, XPS were used to characterize graphene oxide aged for 2 years. The results showed that after aging, the C/O ratio of graphene oxide increased from 1.96 to 2.76, but the type of oxygen-containing functional groups did not change. In addition to oxygen-containing functional groups, the content of -CH3, -CH2- and physically adsorbed water also decreased. The change in the structure is manifested by the reduction of the average interlayer distance from 1.320 nm to 1.134 nm. Moreover, ID/IG increased from 0.95 to 1.03, indicating that the defect density in the carbon skeleton increased after aging. The thermal decomposition process of graphene oxide and its decomposition products were analyzed by thermogravimetric combined with Infrared spectroscopy. When the temperature exceeds 60°C, the infrared signal of CO2 produced by the decomposition of graphene oxide can be detected. After aging, the decomposition peak temperature of graphene oxide decreased from 216 to 195°C. The amount of CO2 produced in the decomposition products is almost unchanged, while the amount of CO and H2O produced decreases, and the amount of SO2 produced decreases significantly. The OH radicals and heat accumulated during the decomposition process may in turn accelerate the decomposition rate, leading to a thermal runaway process at 216°C.