Lignin　is　a　sustainable　biomass　resource　with　abundant　hydroxyl　groups　that　holds　great　promise　for　use　as　a　feedstock　for　polyurethane　foam　production.　Therefore,　the　flexible　polyurethane　foams　(FPUFs)　were　prepared　using　the　oxidized　alkali　lignin　(OAL)　as　the　matrix　to　enhance　its　compatibility.　The　OAL　was　obtained　under　the　following　conditions　of　60　degree　celsius,　80　min　treatment,　a　ratio　of　hydrogen　peroxide　to　lignin　of　1.2:1,　and　a　ratio　of　iron　hydroxide　to　lignin　of　0.01.　It　was　demonstrated　that　incorporating　OAL　enhanced　the　density,　compressive　strength,　sound-absorbing　performance　and　degradability　of　foam　composites.　The　compressive　strength　was　also　improved　by　more　than　five　times　than　that　of　blank　foam　under　the　optimal　conditions,　reaching　0.11　MPa.　The　thermogravimetric　analysis　(TGA)　revealed　that　the　foam　composite　containing　30　%　modified　lignin　content　exhibited　the　highest　thermal　stability.　The　results　of　solvent　resistance　testing　demonstrated　the　durability　of　the　foam　composites　in　both　water　and　solvents.　Lignin-modified　polyurethane　foam　exhibited　an　acoustic　absorption　coefficient　above　0.2　across　a　wide　frequency　range,　with　the　highest　value　reaching　0.84,　meeting　the　conventional　requirements　for　sound　absorption　materials　(alpha　＞　0.2).　The　results　suggested　that　this　environmentally　friendly　preparation　method　was　feasible　for　producing　high-performance　polyurethane　foams,　which　was　appropriate　for　the　production　of　sound　absorption　boards　for　industry,　transportation　by　train　and　automobile.