Abstract: The tool setting accuracy is one of the main factors that affect the surface shape accuracy of the workpiece. In order to achieve the high-precision tool setting plane or spherical parts in the ultra-precision turning process, an optical tool setting system based on CCD sensor is designed. Through the combination of LVDT tool setting device coarse positioning and optical tool setting device fine positioning, the center height of the tool and the arc half of the tool tip can be quickly and accurately measured. Accurate tool setting is completed, and repeated tool setting accuracy reaches 1 μm. The tool setting device is applied to SGDT350 machine tool, which is a self-developed three-axis diamond lathe. The super precision machining of convex spherical aluminum parts with a diameter of 75 mm and a top ball diameter of 250 mm is realized. The surface precision PV of the device is 0.24 μm.the accuracy of the tool setting device and the effectiveness of the method are further proved, and the efficiency of tool setting is greatly improved.