Due　to　the　huge　demand　for　as　well　as　the　limited　reserves　of　fossil　resources,　renewable　biomass　that　can　be　converted　into　chemicals　has　become　a　global　research　focus.　In　this　paper,　cornstalk　residue　was　liquefied　using　a　mixture　of　polyethylene　glycol　with　a　molecular　weight　of　400　g/mol　(PEG400)　and　ethylene　carbonate　(EC)　as　the　liquefaction　reagent　and　5-sulfosalicylic　acid　(SSA)　as　the　catalyst.　The　liquefaction　product　of　the　cornstalk　residue　(CRL)　was　used　to　replace　petroleum　polyols　to　prepare　flexible　polyurethane　foams.　The　results　showed　that　the　optimum　liquefaction　conditions　were　as　follows:　PEG400/EC　was　7.5:2.5　(w/w),　the　ratio　of　liquid/solid　was　5:1　(w/w),　the　liquefaction　temperature　was　160　C,　the　mass　of　SSA　was　4　g,　and　the　liquefaction　time　was　60　min.　The　hydroxyl　number　and　residue　content　of　the　CRL　at　optimal　conditions　were　315.7　mg　KOH/g　and　4.5%,　respectively.　The　compressive　strength　and　apparent　density　of　the　polyurethane　foam,　which　was　prepared　by　90　wt%　CRL,　10　wt%　commercial　polyether　GE-220,　and　methylene　diphenyl　diisocyanate,　were　205.6　kPa　and　0.075　g/cm3,　respectively.　©　2019　North　Carolina　State　University.