Abstract: A filter lens, an LED lamp with the filter lens, and an illumination system, the illumination system comprises an LED lamp with a filter lens, and an illuminated surface. The LED lamp with a filter lens comprises a light-emitting module, a collimating lens, and a filter lens, the filter lens comprises a light incident surface, and a light-emitting surface disposed on an opposite side of the light incident surface. The light incident surface comprises a plurality of irregular slot arranged end to end. Since the illumination system uses the LED lamp with a filter lens, and the filter lens of the LED lamp with the filter lens comprises the above-mentioned irregular slot, to adjust the positional relationship between the LED lamp with a filter lens and the illuminated surface.