Loess　subgrade　is　easy　susceptible　to　moisture　damage,　especially　in　the　embankment　at　the　bridge　approach.　In　order　to　decrease　the　differential　settlement,　Caster　oil-based　polyurethane　(COP)　was　used　to　reinforce　the　loess　embankment.　The　adhesive　performance　and　impermeability　mechanism　of　COP　reinforced　loess　embankment　using　grouting　technology　were　investigated.　The　adhesive　force　of　COP　reinforced　loess　embankment　is　bigger　than　tranditional　polyurethane　(1.5　MPa).　The　bond　strength　of　loess　embankment　sample　is　very　low　and　lower　than　0.15　MPa,　while　the　bond　strength　of　COP　reinforced　loess　embankment　sample　is　bigger　than　0.32　MPa.　The　adhesive　performance　results　showed　that　COP　could　improve　the　wet　resistance　and　adhesive　performance　of　loess　embankment.　The　new　permeability　model　of　COP　was　proposed　and　it　showed　that　the　loess　particles　were　covered　by　COP　with　the　addition　of　COP　and　water　can　not　immer　into　the　loess　pores,　and　COP　permeability　appeared　gradient　and　consisted　with　diffusion,　permeate,　and　compaction　three　stages.　Firstly,　the　COP　grouting　material　fills　the　void　of　soil　to　form　a　cylinder　and　form　a　network　structure.　Then　squeeze　the　broken　loose　soil　to　form　a　semicircular　projection,　forming　the　water　stop　channel;　Finally,　the　dense　soil　is　split　to　form　a　cone,　forming　the　COP-loess　soil　consolidation.　©　2022　Elsevier　Ltd