The configuration of torus sparse aperture is introduced, and its modulation transfer function (MTF) is derived from its pupil function. MTF is simulated by Matlab software under different internal and external diameter ratios of torus sparse aperture; an example of torus sparse aperture is designed by Zemax software, from which the MTF is obtained and compared with the above simulation results; the imaging capability of torus sparse aperture is evaluated using the standard discrimination plate as the target object. The results show that the cut-off frequency of torus sparse aperture depends on the external diameter, and the MTF curves become steeper in low frequency area as the internal and external diameter ratio e increases. Imaging results also reveal that images′ peak signal-to-noise ratio (PSNR) decreases when the ratio e increases, and images′ details are enhanced with their contour information being kept in a better way when the fractional differential operator is utilized to enhance the image quality.