Taking 6309 bearing inner circle of GCr15 material as the research object, the influence law of ultrasonic assisted vibration on abrasive grain motion trajectory, surface roughness, roundness and micro-morphology during high speed ultrasonic grinding was investigated. Based on the theoretical simulation of the abrasive grain cutting trajectory of ultrasonic inner circle grinding and the influence of ultrasonic amplitude and grinding wheel speed on the trajectory, a theoretical model of grinding removal and grinding surface roughness was established to analyze the changing trends of surface quality and grinding efficiency during high speed grinding. Through an ultrasonic grinding test on the bearing inner circle, the influence of process parameters on inner circle surface quality at high speed (16 000-22 000 r/min) was studied and the theoretical model was verified. The contact trajectory between the abrasive grain and the inner circle became longer with the increase of the ultrasonic amplitude, but the intensity of the abrasive grain cutting trajectory also decreased with the increase of the grinding wheel speed. The increase of the ultrasonic amplitude and the grinding wheel speed could increase the cutting removal and reduce the roughness. Compared with brown corundum and white corundum with the same parameters, the surface quality of the GCr15 bearing after grinding the inner circle with a chrome corundum 100# ceramic bonding wheel was superior, and the variation trend of surface quality under a single factor was consistent with the theoretical analysis. In conclusion, with the same grinding parameters, ultrasonic grinding with 1.5 μm amplitude can reduce the inner roundness to 0.92 μm and the roughness to 130.5 nm, which can reduce the roughness up to 41.5% and roundness up to 52.6% compared with the traditional grinding with the same parameters. Through the orthogonal test, it is concluded that the factors that have a great influence on the surface quality after grinding at high speed of the grinding wheel are as follows:grinding wheel speed, ultrasonic amplitude, feed speed. The optimal grinding process for this research object at high speed is as follows:grinding wheel speed 20 000 r/min, radial feed speed 600 mm/min, axial amplitude 1.5 μm, workpiece rotation 250 r/min, grinding depth 20 μm. Based on the optimal process obtained by orthogonal test, single factor tests are carried out on grinding wheel speed, ultrasonic amplitude and feed speed. According to the decline percentage of the single factor tests, the improvement effect of ultrasonic grinding on surface quality increases with the increase of grinding wheel speed when the speed is less than 20 000 r/min, and decreases with the increase of rotating speed when the speed is more than 20 000 r/min. When the radial feed speed of the workpiece is less than 600 mm/min, the improvement effect of ultrasonic grinding on the surface quality increases with the increase of the feed speed, and decreases with the increase of the feed speed when the radial feed speed is more than 600 mm/min. When the axial ultrasonic amplitude is applied to 6 μm, a sinusoidal vibration pattern will appear on the surface after grinding and the grinding effect will be weakened, while the uniform surface texture after 1.5 μm grinding can effectively reduce the cracks caused by high speed grinding.