The present invention relates to a novel method for preparing a catalyst for partial oxidation of methylbenzenes, comprising, (a) a step of preparing a solution or slurry of the compounds comprising tungsten; (b) a step of supporting the solution or slurry obtained in the step (a) on inorganic carrier; (c) a step of drying the catalyst obtained in the step (b); and (d) a step of calcining the dried catalyst obtained in the step (c), characterized in that the ratio of the pore volume of inorganic carrier and the volume of the solution or slurry in the step (b) is 1:0.9.about.1.1, and the catalyst provides superior aromatic aldehydes selectivity to those prepared by the conventional impregnation or heat evaporation method over a wide range of conversion rate.