The conventional curved bionic compound eye relay system is required to undertake the task of converting the curved image plane caused by the splicing of large-field subeyes into a flat image field, which poses certain difficulties to the system design. A method was proposed for the splicing arrangement of the flat image plane of the large-field compound eyes, and the method was described mathematically. By constructing a balanced model between the number of subeyes, the total field of view of the system and the subsequent reasonable selection of the optical relay system parameters, the relationship between the depth of field of the relay system and the optical range difference of the spliced image plane of the compound eye was analysed, and it was concluded that the optical range difference generated by the splicing method of the compound eye flat image plane was within the acceptable depth of field of a typical optical relay system, which could effectively reduce the design pressure of the relay optical system. Based on the above theory, a compound eye optical system with a field of view of 16° for a single subeye and an overall field of view of 96° was designed for practical verification. The system finally achieves an aberration of less than 2%, the transfer function reaches the diffraction limit in the central field of view and the edge field of view is close to the diffraction limit with good image quality, which proves that splicing theory is feasible.