Provided in an embodiment of the present invention are a method and device for beam sidelobe suppression. The method comprises : determining, according to a desired direction of a main beam, a first forming weight of an intelligent antenna; determining, according to the first forming weight, a forming pattern of the main beam; determining, according to the forming pattern of the main beam, a beam suppression feature quantity of a sidelobe to be suppressed, wherein a phase in the beam suppression feature quantity is opposite to a phase of the sidelobe to be suppressed; determining, according to the beam suppression feature quantity, a second forming weight; and generating, according to the first forming weight and the second forming weight, a beamforming weight of the intelligent antenna. In the present invention, weighting processing is performed on a second forming weight corresponding to a side beam and a first forming weight corresponding to a main beam to realize suppression of a sidelobe of the main beam. The method for sidelobe suppression provided in the embodiment of the present invention does not cause mainlobe widening and has high practicability and reliability.