Abstract: SiC fiber reinforced SiC ceramic matrix composites (SiC_f/SiC) have problems such as poor machining quality and severe tool wear. To study these problems, SiC_f/SiC composites were processed by ultrasound-assisted grinding, and the grinding force, surface morphology and three-dimensional surface roughness were tested and explored. The removal mechanism of materials in ultrasound-assisted grinding was analyzed. The results show that ultrasonic assisted grinding can effectively reduce grinding force. The ultrasonic effect promotes the fracture of SiC fibers and the formation of shorter fibers to be removed, which reduces the fiber breaking and peeling and improves the surface quality, but the large amplitude of vibration is not conducive to the improvement of the surface quality.