Combining fractional Fourier-domain filtering with optical imaging, a two cascade fractional Fourier transform (FRFT) optical imaging system with filtering aperture is proposed, which is based on Lohmann I single-lens system. Firstly, the basic theory of the FRFT optical imaging combined with the fractional Fourier-domain filtering is discussed according to the relation between FRFT and Fresnel diffraction as well as fractional additivity of FRFT. Then, imaging performance for distant objects is discussed in terms of different orders, the relative sizes of filtering aperture and pupil, based on the point spread function (PSF) and modulation transfer function (MTF). The results show that, compared with the traditional Fourier optical imaging, some FRFT optical imaging systems based on fractional Fourier-domain filtering have better imaging performance and higher resolution.