In order to achieve the fine analysis and classification of the defects on the panel, the apochromatic objective with a numerical aperture of 0.42 in the visible spectrum and illumination optical system were designed. First, the objective lens was designed with reasonable structure optimization, optical focal length distribution and material selection, and the MTF curve is closed to the diffraction limit. Secondly, the illumination optical system is designed by the scheme of Kohler illumination. Simulating optical system with Lighttools software.The experimental results show that the resolution of the optical system can reach 0.775 μm and the illumination uniformity can reach 98%. The results are consistent with the actual test results and meet the requirements of high-precision panel inspection.