Optical synthetic aperture imaging system applies the interferometric method to sample object in the spatial frequency domain and retrieve the image whose spatial resolution is much higher than that of monolithic aperture by inverse Fourier or other numerical transformation. An optimized synthetic aperture array which is composed of a number of identical sub-aperture located at a circle can provide a roughly uniform distributed and no-redundant sampling coverage in two-dimensional spatial frequency domain, which can form a high quality and snapshot imaging system. An optimization method called simulated annealing is adopted for the optimization of a two-dimensional circle aperture array composed of 7～16 sub-apertures. Based on principle of optical diffraction imaging, imaging characteristics of the optimized arrays as well as arrays distributed evenly composed of N sub-apertures at a two-dimensional circle are analyzed in detail by using computer simulation in both spatial domain and frequency domain. The simulated computation results of the arrays composed of 7～16 sub-apertures show that the optimized array has better quality of image than the arrays of distributed sub-aperture in both point spread function and optical transfer function. Besides, the bigger the size and the more the number of sub-aperture, the better the imaging is. But, on the other hand, although higher resolution can be obtained with bigger size of the circle synthesized by a number of sub-aperture, improved imaging quality is refused.