A light cutter device. The device uses a fan to produce airflows flowing through a cylinder-like or core-like lamp reflector so as to form a wake region downstream of the lamp reflector. A front light cutter is placed on the wake region, and an upper light cutter and a lower light cutter are respectively installed at both sides of the lamp reflector. One end of the light cutters is mounted at a lamp housing by bolts, and the other end maintains a distance from the lamp reflector and extends to the back end of the lamp along the contour of the lamp reflector. The light cutters are able to shelter the bright light beam, emitting from the lamp, towards the outlet of airflows to not leak out of the projector and lead airflows to cool the lamp reflector. As a result, there is no need to install a decline guide on the airflows for sheltering the light so that the block o the airflow outlet decreases.