In order to improve the present accuracy and speed of XLPE cable materials impurity testing, we set up the impurity testing system using the TCD132D chip and design the hardware driving circuits. Process the acquisition data using the virtual oscilloscope DSO2902. The method can discriminate whether the impurity particles exist or not effectively. The result shows that this system can measure the size of impurity particles of XLPE cable materials correctly, it also can find out the accurate location and numbers of impurity particles. The resolving power of this method can reach 20 µm and the error is less than 10%.The possibility that the impurity particles can be checked out is up to 100%.