The work aims to explore the surface damage characteristics of the workpiece in the compressive prestress ma-chining process of engineering ceramics in combination with ultrasonic vibration machining method. An engineering model of ultrasonic vibration assisted machining process of engineering ceramics under compressive prestress was established. Based on the discrete element simulation results and experimental results of Al2O3 ceramic scratch process, the machined surface was observed by scanning electron microscope, and the scratch force was measured by three-dimensional dynamic piezoelectric dynamometer. The fracture of groove profile showed a periodic trend during the ultrasonic vibration under compressive prestress and the materials pilling up on the edge of the scratching-groove were constrained. When the prestress was 200 MPa and scratching depth was 10 μm, the actual scratching depth and groove width of normal scratching process were 7.58 μm and 107.5 μm, respectively, while those of ultrasonic assisted scratching process were 8.55 μm and 143.5 μm. With the simulation results, the ultrasonic assisted scratching process could decrease the number of radial cracks, but increase the depth. What’s more, the tangential forces of the both scratching processes showed obvious discrepancy. The ultrasonic assisted scratching process had the lower tangential force which fluctuated more steadily. Ultrasonic vibration assisted machining process can reduce the cutting force in the prestress machining process of engineering ceramics and improve the machining efficiency of materials.