Synchronous belt is a kind of belt drive which uses the meshing of belt teeth and belt gear teeth to transmit power. In CNC machine tools, the purpose of using synchronous belt. To make the transmission more precise. When the CNC machine tool is working, the servo motor or stepper motor is driven by the pulse power supply, and the rotating 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 appears fracture, wear, bearing layer elongation, pitch increase and other problems, it will affect the precision of the CNC machine tool machining parts, and even lead to the damage of the machine tool.