Different from the conventional spherical compound eye imaging system, a novel optical design structure was proposed that the non-homogeneous microlens array was fabricated on the spherical substrate. The whole array was arranged as symmetrical circle pattern, and the focal length of microlenses arranged along the radius direction was decided by its position and equal to the distance between substrate and photo-detector. According to the imaging theory of geometrical optics, the design parameters of microlens array were computed and verified by ray tracing procedure. From the simulated results, we can get the conclusion that the optimal design structure of single-layer spherical compound eye can focus the whole field of vision on the photo-detector and improve the imaging quality of the edge field of vision obviously. Moreover, the fabrication technology of non-homogeneous microlens array on spherical substrate is discussed.