The invention relates to the technical field of radar detection, in particular to a device for real-time detection of spectrum from airborne hyperspectral imaging LiDAR and method thereof. The device comprises a laser and a reference module; the reference module comprises a first reflecting mirror and a second reflecting mirror with a given transmittance; the first reflecting mirror and the second reflecting mirror are arranged with a focusing mirror and an optical fiber in sequence therebetween. The laser emits a laser light to the first reflecting mirror with a given transmittance, and the beam of the laser light transmitted through the first reflecting mirror after passing the focusing mirror is used as the reference beam after passing the optical fiber. The invention enables detection of the spectral line of each pulse and improves the precision of reflection spectrum of the ground object measured by the system.