Arc discharge is a physical phenomenon that often occurs during the make and break process of the switches.The high temperature characteristic of arc has great harm for the performance and reliability of the contacts.Due to the extremely short arcing time and high temperature, direct observation about arc is almost impossible.Consequently, the arc visual detection has become one of the main research directions.CCD, CMOS and optical fiber array are the main test methods of arc, and have their own advantages and disadvantages.CCD and CMOS have high temporal and spatial resolution, but the arc chamber is generally opaque, a window must be open in the inner wall of the arc chamber to obtain the arc movement images, therefore, the arc parameters and the arc chamber pressure will have a certain change compared with the original prototype.The method of optical fiber array does not need to destroy the structure of the arc chamber, however, due to the restrictions by the number of optical fibers, the spatial resolution of the optical fiber array equipment is lower than CCD and CMOS.Keeping the product in the original state as much as possible, the arc movement images of contact are captured by the high-speed camera device in this paper.Combining Image-Pro Plus with Matlab software, the breaking arc images of magnetic latching relay are processed, and the total pixel values of arc images are calculated to complete the numerical representation of the arc morphology.