Synthetic aperture ladar (SAL) can achieve long distance objects high resolutions imaging. However, the mapping bandwidth is generally small, which probably limits its applications in land surveillance. In order to solve the problem, practical imaging range of a wide swath SAL is suggested and a wide swath SAL using non-symmetric beam-pattern illumination with short azimuth size and long range size is investigated in detail. By wave optics diffraction theory, detailed theoretical descriptions of the image formation theory on the wide swath SAL as well as the mathematical simulations are given. The results show that due to the characteristic of short optical wavelength, the conventional image formation theory used in SAL data processing is approximately applied in wide swath SAL using non- symmetric beam- pattern illumination, that is, range compression by Fourier transformation and azimuth image focusing by matched filtering.