Ultrasonic vibration can reduce honing forces efficiently. As the honing wheel can be washed by ultrasonic cavitations of cooling liquid, its jams are decreased and the higher honing efficiency has obtained. Therefore, the combination of ultrasonic machining and gear honing is a method for gear fine machining with its wide application future. In the paper, to improve the rigidity, the ultrasonic vibration system adopted the structure of double supports as traditional honing machine, so the horn is symmetric. The machined gear was simplified into a circular thin plate with diameter of its reference circle and the horn was treated as its half as the symmetry; the frequency equations of the transformer were derived according to stress match under the condition that the half horn and plate of the transformer were considered at the same time; the frequency equations were derived based on the boundary conditions. Then the design parameters of the transformer were obtained as the frequency equation was solved computationally and expanded to the whole horn. The displacement, stress of the transformer was solved, too. Finally, the vibration mode of the transformer was analyzed by ANSYS. The results of theoretical and ANSYS analysis is consistent, which means the theoretical model and analysis method are correct.