The invention discloses a lightweight combined-type plate structure used for low-frequency noise insulation. The lightweight combined-type plate structure is composed of a noise insulation substrate, beam piece units and supporting members. The beam piece units are fixedly connected on the noise insulation substrate through the supporting members, each beam piece unit comprises at least one cuboid-structured beam piece, and central points of the beam pieces are fixedly connected with the corresponding supporting members; the minimum order resonance frequency of one beam piece is identical with one target noise frequency. The design method includes the steps 1), respectively determining design parameters according to number of target noise bands; 2), determining a structural parameter of the noise insulation substrate; 3), when determining periodic spacing a, selecting the same within the range of 0