Abstract: This paper makes research on the machining of engineering ceramics with form surface,then introduce the design of ultrasonic grinding device of its structure,its amplitude transformer and its combined system in detail,and puts up a mathematical model about the design of amplitude transformer which is applied at numerical control machine tool.In the end,on the base of the work,a virtual example was validated,and the two results agree with each other fairly well.The method has been used in virtual design and has a good purpose.