The invention provides a magnetic core-shell structural solid acid material and a preparation method thereof. The method comprises the following steps: synchronizing magnetic iron oxide by the coprecipitation method; adding vinyl trimethoxy silane to perform hydrolytic condensation to form a magnetic iron oxide core with two bonds on the surface; mixing and copolymerizing a double-bond containing sulfoacid compound monomer and surface-alkenylation magnetic iron oxide core to obtain a core-shell structural solid acid material catalyst. The catalyst is high in heat stability, stable in water, can be in contact with acidic center easily, is high in acid value, and good in catalyzing effect, and can be magnetically absorbed and recovered, and the recycling is simple and convenient.