Tool magazine and automatic tool changer are key functional components used for storing and exchanging tools of CNC machine tools. Their performance condition, especially the tool change accuracy, directly affects whether CNC machine tools can accurately and quickly complete tool change. They are key factors that affect the reliability of CNC machine tools. By setting up the tool change accuracy test bed of the tool magazine and automatic tool changer on CNC machine tools, the measuring method for tool changing accuracy is proposed based on two laser displacement sensors. Then, the positioning parameter calibration method of the laser displacement sensor is proposed by means of the position of machining center workbench, which can be precisely controlled by the numerical control system. By developing the tool change accuracy test method, one million tool changing tests are implemented to reveal the change rule of the tool change accuracy of the tool magazine and automatic tool changer with load and test times, and the change law of the precision of the holder before the insert, before the broach and after the broach. In this way, an important reference is provided for how to reduce the influence of the tool holder on the spindle in the process of the insert.