The principle of micro-zooming is analyzed in the spatial domain. Micro-zooming is the method that changes imaging focal length of the optical system gradually to obtain a series of images of the same scene with different amplified multiples, and reconstruct a high resolution image through these images. It can be used to realize superresolution imaging of opto-electronic imaging systems. Micro-zooming imaging can be equivalent to change the area and position of the sensor element's corresponding object radiance distribution region, which are related to the magnification and the location of the sensor elements respectively. So the spatial model can be established and the relationship between the observed images and the ideal high resolution image can be given as linear equations. The high resolution image can be obtained by solving the equations. The experiment of the superresolution imaging of area-array CCD by micro-zooming is described in the end of the paper. It denotes that the resolution of the image increases markedly.