Synchronous belt is a kind of belt transmission which uses the meshing of belt teeth and belt teeth to transmit power. In the numerical control machine tool, the purpose of using synchronous belt. This is to make the transmission more accurate. When the CNC machine tool is working, the servo motor or stepping motor is driven by the pulse power supply, and the rotary motion of the motor is transformed into the linear movement of the tool holder through the synchronous belt. Therefore, the synchronous belt plays a vital role in the CNC machine tool. If the synchronous belt has problems such as fracture, wear, bearing layer elongation, pitch increase and so on, it will affect the accuracy of the parts processed on the CNC machine tool, and even lead to the damage of the machine tool.