The invention relates to a rectangular aperture telescope antenna for a synthetic aperture laser imaging radar, which comprises an objective lens pupil, an objective lens, an eye lens and an eye lens pupil. The objective lens pupil is positioned on the front focal plane of the objective lens; the eye lens pupil is positioned on the back focal plane of the eye lens; the objective lens pupil, the objective lens, the eye lens and the eye lens pupil have rectangular apertures; the focus of the objective lens is f1; the focus of the eye lens is f2; and the distance between the objective lens and the eye lens is f1+f2. The invention can generate a rectangular optical toe according with the scanning mode of the synthetic aperture laser imaging radar, eliminate the phenomenon of uneven imaging resolution and reduced resolution of the optical toe in the azimuth direction and the vertical motion direction, and design optimal scale of the rectangular apertures to respectively control the scale of the laser radar optical toe in the azimuth direction and the vertical direction motion, so as to obtain large scanning width and high azimuth direction resolution.