Cf/C-SiC composites possess high strength, high hardness, high thermal conductivity, and low density, making them ideal for aerospace, aero-engine parts, and high-temperature molten metal processing equipment. In these composites, carbon fibers provide crucial structural support and reinforcement. However, achieving the required surface quality for practical applications imposes stringent criteria. Scratching is one of the promising techniques to obtain smooth surfaces, but the cutting mechanism is altered due to the presence of carbon fibers. Additionally, the anisotropic structure of these composites complicates the interaction between the workpiece and abrasive particles compared to isotropic materials, leading to potential surface quality deterioration. Conducting scratch experiments is essential to explore the interaction between materials and abrasive grit, aiding in understanding material behavior during machining and optimizing the scratching process. This study investigates the abrasive-workpiece interaction mechanism in 2.5D needle-punched Cf/C-SiC composite scratching tests. The interaction between the composites, fibers, and abrasive grit was examined in depth by systematically varying parameters such as scratching speed, depth, and angle in diamond grit scratching experiments. The experimental results indicated that the composites exhibit different scratching behaviors under various parameters, involving complex mechanisms such as friction, wear, and thermal coupling between fibers and abrasive grit. Analyzing these results led to the proposal of optimized scratching parameters aimed at maximizing material removal rate, improving surface quality, and extending tool life. The study’s findings provide deeper insights into the key factors of the abrasive-workpiece interaction mechanism in composite materials, benefiting grinding processes, surface quality, and other machining or design aspects.