Abstract: C_f/SiC ceramic matrix composites are critical materials for aerospace hot-section components, yet their high hardness and brittleness pose significant machining challenges. Laser-assisted ultrasonic grinding is an effective solution for this machining difficulty, but its underlying mechanism remains unclear. To reveal the material removal mechanism of laser-assisted ultrasonic grinding for C_f/SiC, this study prefabricated multiple ablation grooves using a continuous laser beam and comparatively analyzed the surface morphology under conventional grinding, ultrasonic-assisted grinding, and laser-assisted ultrasonic grinding. Results indicate that laser irradiation generated ablation craters surrounded by peripheral ridges and outer deposition zones. Both conventional grinding and ultrasonic-assisted grinding exhibited predominantly brittle removal mechanisms, accompanied by surface damage such as matrix fragmentation and fiber tearing. In contrast, laser-assisted ultrasonic grinding combined brittle fracture with plastic removal, inducing cracks that preferentially propagated along the axial direction. The resulting debris primarily consisted of short fibers and matrix fragments, significantly improving surface quality. This study demonstrates that laser-assisted ultrasonic grinding effectively suppresses machining damage and enables low-damage machining of C_f/SiC.