C/SiC composite is a typical material difficult to machine. It is hard and brittle.In machining, the cutting force is large, the material removal rate is low, the edge is easy to collapse, and the tool wear is serious. In this paper, the grinding of C/SiC composites material along the direction of fiber distribution AUAG is studied respectively.The surface microstructure and mechanical properties of C/SiC composites processed by ultrasonic machining were evaluated. The change of surface quality with the change of processing parameters was studied. The experimental results demonstrate that the optimal surface quality can be obtained through the optimization design of AUAG ultrasonic grinding parameters.