Abstract: In order to prepare a light mass and efficient sound insulation composite, the nitrile rubber(NBR) and polyvinyl chloride(PVC)were blended as the main ingredients and the high-density metal particles (HMP)/NBR-PVC microporous damping composite were prepared by one step molding foaming process. The effect of rubber-plastic mass ratio on the cell structure, damping performance and sound insulation performance of composite materials were studied by SEM, dynamic thermomechanical analysis and the impedance tube measurement. The sound insulation mechanism of HMP/NBR-PVC microporous damping composite was further analyzed. The results show that the presence of microporous structure increases the sound energy attenuation during the propagation inside the composite and improves the sound insulation performance of microporous composite material. The HMP/NBR-PVC microporous damping composite with the NBR and PVC mass ratio of 50:50 displays good cell structure, mechanical properties and damping properties. Its sound insulation index is up to 28.1 dB. The rubber-plastic microporous damping composite shows the advantages such as light mass, soft and easy to process. It has guidance for the development and application of new type sound insulation materials.