The invention relates to a magnetic carbonaceous solid acid catalyst and a preparing method thereof and application thereof in preparing levulinate. The method includes the steps of firstly, sufficiently dissolving dry paper pulp fiber in a ferric salt solution, conducting stirring and evaporating water to dryness, and then conducting drying to obtain a precursor loaded with ferric salt, wherein the mass molar ratio of the dried paper pulp fiber to the ferric salt is 5-25 g to 0.01-0.1 mol; secondly, conducting high-temperature carbonization on the precursor loaded with the ferric salt under the inert atmosphere to obtain a paper-base magnetic carbon compound; thirdly, mixing the paper-base magnetic carbon compound and concentrated sulfuric acid according to the ratio of 1 g to 10-30 ml, conducting a sulfonation reaction, and conducting washing and drying to prepare the magnetic carbonaceous solid acid catalyst. The prepared catalyst is efficient and stable, low in cost and high in catalytic activity in an alcoholysis reaction, the catalyst and the reaction solution can be effectively separated through a magnet after the reaction ends, the redundant filtering or centrifuging process is avoided, and the repeated utilization rate is high.