Currently, research on hydrogen-based shaft furnaces mainly focuses on the reduction thermodynamics and kinetic processes and furnace structure design, while research on refractories is rare. Based on the strong reducing environment of H2/CO mixed gas, this study simulated the service conditions of atmospheric pressure hydrogen-based shaft furnaces, and researched the performance changes and instability mechanisms of typical Al2O3-SiO2 refractories after reduction treatment. The results show that under the condition of V(H2)∶V(CO)=5∶2, the heat treatment temperature rises from 450 ℃ to 950 ℃, and the reduction ability of mixed gas to Al2O3-SiO2 refractories is gradually enhanced. Under current conditions, the two key factors leading to the instability of Al2O3-SiO2 refractories are the Fe2O3 content and the phosphate binder. 1) When the Fe2O3 content in Al2O3-SiO2 refractories is high, it is easily reduced to elemental iron in the H2/CO atmosphere. At the same time, this situation will lead to a certain degree of volume change and significant decrease in mechanical properties of Al2O3-SiO2 refractories. 2) Phosphate-bonded Al2O3-SiO2 refractories materials also face phosphate volatilization, leading to an increase of apparent porosity and a decrease in structural stability. However, it is found that when the Fe2O3 content in the phosphate-bonded alumina-mullite brick is lower and accompanied by a certain amount of TiO2, the refractories exhibits good resistance to H2/CO gas reduction. By comparing the mechanical properties of Al2O3-SiO2 refractories in CO atmosphere and H2/CO atmosphere, it is found that the heat treatment condition which holding 3 h at 850 ℃ in the atmosphere of V(H2)∶V(CO)=5∶2 has a stronger reducing ability than the heat treatment condition which holding 100 h at 500 ℃ in CO atmosphere.