The modulation transfer function (MTF) of a sparse-aperture system is lower than that of a filled-aperture system within the cut-off frequency. The zero values of MTFs may be produced at some mid-spatial frequencies, which affects the image quality. Configuration optimization of sparse-aperture systems can achieve a sparse-aperture configuration with more uniform MTF. A criterion is given to optimize the sparse-aperture system, which is directly linked with the maximum spatial frequency ρR (or practical resolution) and the diameters of the sub-apertures. Optimal configuration of dual three sub-apertures and the image simulations are obtained. Wiener filter technique is applied. The image simulations and the MTFs comparison of optimized configuration and un-optimized configuration of dual three sub-apertures show that configuration optimization is a key aspect of the design for sparse-aperture systems. The optimization criterion of sparse-aperture systems is reasonable and the image quality can be improved by optimizing configuration.