Traditional synthetic aperture radar uses wideband signal to achieve range resolution, and uses one-dimensional synthetic aperture to achieve azimuth resolution, thereby forming a two-dimensional image. In the cases of short range imaging, a very high imaging resolution may be required, and it is difficult to achieve such high resolution using signal bandwidth. A two-dimensional synthetic aperture imaging system is proposed; it uses the two-dimensional synthetic aperture to achieve two-dimensional resolution. The resolution depends on the length of the synthetic aperture, and it is no longer limited by the signal bandwidth and can obtain ultra-high resolution. The transmitted signal is single frequency waveform, thus the system can be very simple. The imaging algorithm for the single frequency two-dimensional synthetic aperture imaging system was derived in detail. Simulation results showed that the single frequency two-dimensional synthetic aperture imaging system is an effective technique for high resolution imaging.