To address the demand for in vivo small animal fluorescence imaging in the near-infrared II （NIR-II） window， as well as solve the problem of simultaneous reuse of multiple wavelengths within a wide spectral range. This study took the perspective of aberration correction and designed an optical system by iteratively refining the lens group structure based on aberration curves. The working distance was increased through reasonable focal length distribution， and the glass material selection was optimized to balance chromatic aberration control and energy transmittance within the wide spectral range. The final optical structure ended up with a focal length of 40 mm， capable of ensuring MTF>0.6@34 lp/mm for the NIR-II spectral band （0.9~2.3 μm） within the working distance range （200~600 mm）， with RMS spot size smaller than the pixel size （15 μm） and distortion less than 1% across the entire field of view. Real-shot tests with resolution targets demonstrate a resolution capability of 50 μm. This optical design provides a solution based on all-glass spherical lenses capable of meeting the requirements for high-quality， low detection threshold in vivo small animal fluorescence imaging in the NIR-II window.