Abstract: By combining Biot theory and Bolton multilayer-panel theory, the calculation formulas of the sound transmission loss (STL) of underwater sandwich plate with poroelastic material are derived, and the sound insulation performances of three constructions (BB, BU and UU) are analyzed. By expressing the acoustic waves in incident field, radiation field and intermediate cavity field with corresponding velocity potential functions, using Biot theory and Bolton theory to describe the transmission process of acoustic waves in poroelastic material, and combining the boundary conditions of the three constructions, the STL of the three models (BB, BU and UU) can be obtained. Among the three models, the UU model has the best sound insulation performance, and the BB model is the worst. The poroelastic material can effectively avoid the standing-wave resonance in cavity, and can significantly improve the sound insulation performance of sandwich plate in high frequency range. Both the thickness of poroelastic material and the thickness of air layer in cavity can effectively promote the sound insulation performance of sandwich structure.