A feed horn for a Low Noise Block down converter is disclosed. The feed horn includes a conical body for gathering satellite signals and a connector coupled to the conical body for coupling the feed horn to a waveguide of the Low Noise Block down converter to transmit the satellite signals to the waveguide. The conical body includes a plurality of corrugations, one of the plurality of corrugations includes a plurality of first openings, and a plurality of second openings, each of the plurality of second openings is formed between the two adjacent first openings, wherein the plurality of first openings and the plurality of second openings are used as slits to induce an interference effect to adjust a beam pattern of the feed horn.