Abstract: A method for preventing feedback light of a laser, includes fusion-splicing a target fiber to an output fiber of a laser, so that laser lights generated by the laser are output from the target fiber. A refractive index of a core of the output fiber of the laser is less than a refractive index of a core of the target fiber. When a feedback light of a laser light of the laser is reversely transmitted to a fusion-splicing surface through the target fiber, total reflection occurs due to a refractive index difference on the fusion-splicing surface, so that the feedback light is transmitted along the transmission direction of the laser light, and is prevented from entering the output fiber along the reverse direction of the laser light and further entering the laser's resonant cavity to damage the laser component or burn out the gain fiber.