To improve the insufficient sound insulation performance of double-layer panel structures at the mass-air-mass resonance frequency, a double-layer panel acoustic metamaterial consisting of a perforated sandwich plate with a porous liner and a homogeneous plate was designed, and the normal sound transmission loss of the structure was calculated by the finite element method. The numerical results show that when the frequency of the perforated sandwich panel with porous lining is tuned to the resonance frequency of the double-layer panel panel, the reduction of the sound transmission loss caused by mass-air-mass resonance is significantly improved. At the same time, the excellent acoustic isolation performance of the conventional double-layer panel structure is maintained at high frequencies. By comparing the sound absorption coefficient and sound transmission loss of perforated sandwich panels and unperforated sandwich panels, it is found that the excellent sound transmission loss of the double-layer panel acoustic metamaterials is attributed to the sound absorption characteristics of the perforated sandwich panels, which is further verified by changing the frequency of the acoustic absorption and the acoustic properties.