The geometric accuracy includes the geometric accuracy of shape, mutual position and relative motion. The surface shape of the workpiece machined on the lathe depends on the relative motion path between the tool and the workpiece, and the tool and workpiece are directly driven by the actuator of the CNC lathe. Therefore, the geometric accuracy of the CNC lathe is the basic condition to ensure the machining accuracy. Each type of digital lathe has its own geometric accuracy requirements. Geometric accuracy generally includes: axial rotation of the main shaft, radial circle runout of the main shaft, mutual perpendicularity of the movement in all coordinate directions, equal height of the axis of the main shaft taper hole and the tailstock taper hole, etc.