An ultra-large-caliber hyperspectral ocean water meter composed of an ultra-large-caliber front telescope system and an ultra-large-field-of-view spectrometer is designed. The front telephoto system uses a coaxial three-reflection optical system structure with a diameter of 4 m, a field of view of 0.64°, a focal length of 21.6 m, and a wavelength range of 400 to 1 000 nm. The large field of view spectrometer uses an improved Offner structure with a field of view of 240 mm and a spectral resolution of 10 nm. The detector pixel size is 15 μm × 15 μm, and four detectors are staggered to achieve a width of 400 km. The ultra-large field-of-view spectrometer is in a wide band of 400 to 1 000 nm, and the root mean square value of the dot chart radius is less than 3.9 μm. The MTF of the entire system of the static orbit hyperspectral ocean water meter is greater than 0.52 at 33.3 lp/mm, and each index meets the application requirements.