Due to the excellent low-frequency acoustic characteristics of the local resonance type phononic crystal plate, related research is becoming more and more abundant. However, most of them were research in the laboratory environment, and there were insufficient researches on the lightweight of its engineering application. Therefore, based on the application background of low-frequency noise in substations, a lightweight design method for local resonance phononic crystal panels was proposed in this paper. Based on this method, a lightweight supercell phononic crystal plate for substation noise frequency spectrum characteristics was designed. The study found that this phononic crystal plate has obvious sound transmission loss peaks at 50 Hz and 100 Hz, and the sound insulation is 67 dB and 48 dB respectively. The sound insulation mechanism was analyzed and studied through the composite sound intensity streamline diagram of vibration mode displacement and sound pressure level. The research in this paper has guiding significance for the engineering application of phononic crystal plate and the noise control of substations in the future.