An optical system for full aperture backscatter diagnose was designed for a novel inertial confinement fusion facility. Several key technologies about optical design were discussed. A wedge mirror with low reflectance was used to attenuate the backscatter lights before diagnosis, so the films of optical elements in the diagnostic system were survived after many shots. A telescope optical system was used to reduce the sizes of the beam as well as the sizes of the optical elements, meanwhile the optical path was folded several times by mirrors to shrink the volume of the whole system. The space filter, dichroic filter, optical filters and colored glasses were combined to simultaneously eliminate the stray light. Moreover, a scatter plate was taken to average the signals to ensure the fiber coupler to obtain needed signals including all wavelengths studied. Based on the analysis of imaging beam structures, a lens was designed for the imaging of parabolic mirror, and a camera was used to record the space distribution of scattered lights on the surface of parabolic mirror. The diagnosis system was designed to provide measurements for scattering time, scattering spectrum, near-field imaging, and scattered energy and its whole sizes are 1.9 m×0.9 m×1.5 m. The full aperture backscatter system designed in this paper has potential applications to the new inertial confinement fusion facility.