The invention relates to a technical method for composite casting of ceramic and a titanium alloy through assistance of variable-frequency ultrasonic waves. The method aims to solve the problem that the ceramic is fragile, and can reduce the stress of the ceramic and avoid cracking of the ceramic. An ultrasonic solidification technology can enable molten titanium alloy to be well combined with a ceramic matrix, the variable-frequency ultrasonic waves assist in the casting process, so that segregation of the titanium alloy in the solidification process is reduced in the casting process, a finegrained area is enlarged, and formation of developed dendritic crystals is reduced; and the ceramic matrix is coated with the molten titanium alloy, so that the crack resistance of the ceramic material is improved. The molten titanium alloy is prepared by adopting a non-consumable vacuum smelting furnace, wherein a titanium alloy bar is made into consumable electrodes, electric arc heat is generated through discharge between the electrodes under the vacuum condition, and the titanium alloy bar is rapidly heated to a high temperature and then melted to obtain the molten titanium alloy. In the casting and cooling process of the molten titanium alloy, due to solidification and shrinkage of the molten titanium alloy, a pressure stress is applied to the surface of the ceramic matrix, and therefore cracks cannot be easily generated in the using process of the ceramic, and the material integrating the advantages of the ceramic and the titanium alloy is obtained.