A dual-wavelength gun aiming collimated beam light source module, comprising: a positioning seat, having a first through hole and a second through hole inside; a first laser module for emitting laser light of first wavelength; a second laser module for emitting laser light of second wavelength; a first reflecting mirror, and the inner surface of the first reflecting mirror has a first wavelength laser light high-reflection coating; and a second reflecting mirror, and the outer surface of the second reflecting mirror has a first wavelength laser light high-reflection coating and a second wavelength laser light high-reflection coating; so as to solve the aiming deviation problem.