A　simulation　model　of　thin　plate　metamaterial　was　established　by　using　finite　element　software　COM　SOL,　and　its　low　frequency　and　wide　band　sound　absorption　mechanism　was　studied　on　the　basis　of　acoustic　siphon　effect.　By　exploring　the　mechanism　of　differential　pressure　acoustic　convergence,　acoustic　impedance　matching　and　negative　dynamic　equivalent　density　under　the　action　of　acoustic　siphon　effect,　the　low　frequency　and　wide　band　sound　absorption　performance　of　the　metamaterial　was　verified.　The　effects　of　parameters　such　as　area　ratio,　sheet　thickness,　and　mass　height　on　the　sound　absorption　properties　of　thin　plate　metamaterials　were　discussed.　Results　show　that　when　a　plane　wave　of　a　certain　frequency　is　incident　on　the　metamaterial,　the　resonance　will　occur　at　a　certain　position　of　the　cell　and　has　the　maximum　sound　absorption.　In　the　case　of　different　area　ratio,　the　metamaterial　still　has　a　relatively　matching　acoustic　impedance.　Almost　all　the　incident　energy　can　be　forced　to　flow　to　the　resonant　cell　to　enhance　the　cell　vibration　and　still　maintain　a　good　sound　absorption　effect.　When　the　thickness　of　the　sheet　becomes　smaller　or　the　height　of　the　mass　increases,　the　peak　frequency　of　the　sound　absorption　coefficient　will　shift　to　low　frequency.　Finally,　the　low　frequency　and　wide　band　sound　absorption　of　underwater　100　-　500　Hz　is　realized　by　reasonably　designing　and　optimizing　the　parameters　of　thin　plate　metamaterials.　©　2022　Chinese　Vibration　Engineering　Society.　All　rights　reserved.