Cassegrain optical remote sensing system is a combination of telescope system and annular aperture. Its Fraunhofer diffraction of infinite objects is the joint result of circular hole diffraction and circular screen diffraction. Because of the loss of diffraction due to central obscuration of circular screen, modulation transfer function (MTF) of the system degrades greatly in middle frequency, and this directly affects the imaging quality. A Cassegrain optical remote sensing system is designed whose focal length is 2 m. In order to make up for the loss of the image quality, a modulation transfer function compensation (MTFC) technology is used, in which the point spread function (PSF) of image is obtained by slanted-edge method, to recovery image. Some assessment functions are used to evaluate the recovery results. The experimental results indicate that the image quality is improved obviously.