Currently,　accelerated　aging　tests　are　widely　used　to　study　the　aging　process　of　polyethylene　pipelines.　However,　this　approach　can　only　simulate　one　or　several　main　influencing　factors　in　the　natural　envi-ronment,　which　are　often　quite　different　from　the　actual　environment　of　the　buried　pipelines.　In　this　study,　five　types　of　PE80　buried　pipelines　in　service　for　9-18　years　were　taken　as　the　research　object,　while　new　PE80　pipelines　were　taken　as　the　reference　group.　The　aging　process　and　mechanism　of　polyethylene　buried　pipelines　were　studied　through　mechanical　and　chemical　property　tests　and　microstructural　analysis.　The　results　showed　that　the　pipeline　exhibited　cross-linking　as　the　main　aging　mechanism　after　being　in　service　for　0-18　years.　The　aging　degree　and　law　of　the　inner　and　outer　surface　of　the　pipeline　were　compared,　and　the　observed　mechanism　of　both　surfaces　was　explained.　After　18　years　in　service,　the　elongation　at　the　break　of　the　pipe　decreased　by　16.2%,　and　the　toughness　of　the　matrix　in　the　main　collapse　area　of　the　tensile　sample　was　the　fundamental　reason　responsible　for　changes　in　the　mechanical　properties.　Finally,　after　18　years　in　service,　the　oxidation　induction　time　of　the　pipeline　was　25.7　min,　which　was　28.5%　higher　than　the　national　standard　value.　There　were　no　potential　safety　hazards　during　continuous　long-term　service.　The　results　of　this　paper　provide　reference　data　and　theoretical　guidance　for　the　aging　process　study　of　buried　polyethylene　pipelines.(c)　2023　The　Authors.　Publishing　services　by　Elsevier　B.V.　on　behalf　of　KeAi　Communications　Co.　Ltd.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/　4.0/).