Abstract: Fiber fracture, matrix smearing, and thermal damage tend to occur during the grinding of short carbon fiber-reinforced thermoplastic composites (SFRTP). To address these issues, tangential ultrasonic-assisted belt grinding experiments were conducted on carbon fiber-reinforced polyamide 6 (CF/PA6). The effects of ultrasonic vibration and grinding parameters on grinding temperature, surface quality, and surface-layer fiber structure were investigated. Meanwhile, a temperature-dependent beam-on-elastic-foundation model was established to analyze the response mechanism of surface-layer fibers. The results show that tangential ultrasonic vibration increases the maximum grinding temperature from 25.0-36.0℃ under the non-ultrasonic condition to 33.6-57.0℃ due to high-frequency friction and viscoelastic dissipation of the PA6 matrix. This temperature rise enhances the tendency for interfacial failure, leading to reduced fiber breakage and increased reorientation response in the surface layer, thereby improving fiber integrity and orientation consistency. Meanwhile, the repeated scratching and enhanced chip-removal effects introduced by ultrasonic vibration are beneficial for reducing surface roughness. Under the conditions of belt speeds of 3-4 m/s, a grinding depth of 0.6 mm, and an ultrasonic amplitude of approximately 45 μm, the surface roughness, fiber integrity, and orientation consistency are all improved. The results can provide process guidance for high-quality grinding of SFRTP materials.