Electric speckle interference experimental system (ESPI) makes use of speckle, which is the carrier of rough surface information, to study a substance. It is a modern optical measuring technique that covers the fields of image processing techniques, laser technology and holographic interference techniques. Due to the splendid coherence of laser, the speckle is so obvious that can be easily and clearly shot by a CCD camera and the data as well as an image attained can be processed by a computer.