Sever plastic deformation (SPD) with high strain rate can increase the material dislocation density, reduce the grain size and improve the mechanical properties. In this paper, ultrasonic compound cutting (UCC) was proposed to improve the efficiency of preparing ultra-fine grained (UFG) pure copper by sever plastic deformation methods. The motion characteristics and strain rate model of UCC were analyzed, and it was concluded that ultrasonic vibration can increase the strain rate in the primary shear zone. According to the 3D FEM equivalent model of UCC, the UCC and traditional compound cutting (TCC) were compared and analyzed from the perspective of strain rate. The simulation results show that ultrasonic vibration can significantly increase the strain rate of chip. The microstructure and mechanical properties of pure copper chip were studied by using a self-developed machining device. The experiment results show that the grain refinement, dislocation density and micro-hardness of pure copper chip were significantly improved in UCC. When the ultrasonic amplitude is 3 µm, the UCC chip grains are about 2.66 µm and the hardness reaches 124 HV, which is about 8% higher than the hardness of TCC chip. The findings of this research provide an important reference for machining UFG pure copper with enhanced mechanical properties.