Abstract: According to the differences between digital transmission electron microscopy with conventional transmission electron microscope in observing and recording a system, we analysed the reasons for the change of magnification of the picture collected by digital transmission electron microscope through the comparison of the differences between the images collected by digital transmission electron microscopy with side-line charge coupled device (CCD) cameras, images observed by the interface view window and electron microscope in magnification. This study enables the teachers and researchers to grasp the exact magnification digital pictures more quickly and intuitively to analyze the results.