In order to solve the problem of long time testing and low precision in the measurement of single slit diffraction experiment，a novel method by using the common camera to construct a photo-electric image measurement system to realize the measurement of the single-slit diffraction experiment illuminated by a laser is proposed. In this method, a camera with USB is used as a measuring tool. The image acquisition and processing software is programmed by using C# software. The automatic measurement of the distance between the ±1st order minimum of the single-slit diffraction is realized based on the algorithm of the image processing. Experimental results show that the proposed method can realize the digitization, visualization and modernization of the traditional single-slit diffraction experiment and also can implement the measurement quickly, effectively and accurately compared with the traditional measurement method. It will allow sufficient time for the student’s theoretical analysis in the experiment. Therefore, this method can effectively improve the students learning efficiency in the experiment.