Large amounts of industrial waste fly ash (FA) have caused serious pollution to the environment. There are a few reports that this kind of material, with its good thermal stability, can be used as a catalyst support for high-temperature catalytic reactions, and it has a certain application space. Upon the alkali treatment of fly ash, its specific surface area is increased, and it has the potential to be a catalyst support. Using treated fly ash as the carrier, a nickel-based catalyst was prepared via a sol–gel method, and the catalytic performance changes of catalysts with different MgO content levels in the dry reforming of methane are discussed. Under the conditions of a space velocity of 1.8 × 10⁴ mL g⁻¹ h⁻¹ and a reaction temperature of 750 °C, in the presence of Ni/NaFA-M2 (M2 = 20 wt% MgO), the CH₄ conversion rate can reach 84%, and it has good reaction stability. This will provide a way to use fly ash and carry out more research.