Electrostatic and magnetic imaging systems have long been widely used in photoelectronic imaging device, such as image converters and image intensifiers, camera tubes and electronic photographic image tubes. But for a long period of time, the design of electrostatic and magnetic imaging systems still remains at the level of direct (normal) method of design, in which the field distributions are calculated by the given electrodes and magnetic coils, the electron trajectories are then computed from the known field distributions, and finally the image position and magnification as well as the aberrations can be determined. The result that we expect is obtained through the method of step by step approximation. This method , of course, is tedious, especially for the design of electrostatic and magnetic imaging systems with variable magnification, the problem becomes much more complicated. In present paper, some inverse designs of realizing different focusing fields for electrostatic and magnetic imaging without image rotation but with variable magnification are investigated, some methods of optimization have been developed, an universal package of programme by using FORTRAN language has been drawn up, an experimental prototype of electrostatic and magnetic imaging intensifier with unsaturated iron medium has been designed, which can produce an image without image rotation but with variable magnification from 0. 3 to 3. 6.