Disclosed are an optical gradation system and method. The optical gradation system comprises: a first device configured to emit broad-spectrum linearly polarized light in a first polarization direction; a second device provided with at least one first region for splitting lights of different wavelengths mixed in the broad-spectrum linearly polarized light incident by the first device into emergent lights in different polarization directions without changing a beam propagation path; a third device configured to filter out linearly polarized light in a second polarization direction from the emergent lights from the second device in different polarization directions; and, a rotator configured to drive at least one of the first device, the second device and the third device to rotate, wherein the first device, the second device and the third device are arranged coaxially.