Micro-perforated absorbers can significantly improve low-frequency sound absorption performance. This paper designs the structural parameters of sandwich composite micro-perforated absorbers, fabricates experimental samples, and conducts experimental research on their underwater acoustic characteristics. The research results indicate that a lower perforation rate leads to a higher resonant sound absorption peak, which shifts towards lower frequencies. The cavity depth not only influences the peak position of cavity resonance but also affects the resonant sound absorption performance of the micro-perforated plate, expanding the sound absorption bandwidth towards lower frequencies. When the number of cavities in the sandwich composite micro-perforated absorber sample is 8, the sound absorption performance is optimal across the entire frequency range. Conical cavities with the same MPP utilization area exhibit better low-frequency sound absorption performance than cylindrical cavities.