The invention relates to a multi-magnification imaging optical system, which comprises a light source and N magnification light paths, wherein the light source can output N light beams with different wavelengths; the N light beams with different wavelengths, which are reflected by an object, are imaged on an image surface through a corresponding magnification light path respectively; when the light source outputs light beams with the first wavelength, light reflected by the object passes through a first magnification light path and is imaged on the image surface; when the light source outputslight beams with the second wavelength, light reflected by the object passes through a second magnification light path and is imaged on the image surface; and the rest may be deduced by analogy, and when the light source outputs light beams with the Nth wavelength, light reflected by the object passes through an Nth magnification light path and is imaged on the image surface. By employing a method for controlling the light source to output the light beams with different wavelengths to image the object on the image surface through light paths with different magnifications, the magnifications are switched, the optical system is light in weight and high in switching speed, the influence of instability and vibration of an electromechanical component on the whole system is removed, the reliability is high, and the energy loss of the light paths is low.