Belonging to the technical field of catalyst synthesis, the invention especially provides a catalyst for preparation of maleic anhydride and a preparation method thereof. The catalyst includes vanadium element, phosphorus element and monodisperse SiO2 microspheres. On the basis of the mass of the catalyst, the mass content of vanadium element in the catalyst is 20-30%, preferably 21-26%; the mass content of phosphorus element in the catalyst is 15-25%, preferably 15-19%; and the mass content of monodisperse SiO2 microspheres in the catalyst is greater than zero and less than or equal to 25%, preferably greater than zero and less than or equal to 10%.