In　order　to　definite　the　failure　mechanisms　and　modes　of　rigid　polyurethane　foam　anti-corrosion　heat　insulating　layer,　field　investigation　and　analysis　of　failure　factors　were　carried　out,　and　the　major　failure　modes　were　drawn.　The　model　of　fault　tree　analysis　(FAT)　for　rigid　polyurethane　foam　anti-corrosion　heat　insulating　layer　was　established,　which　realized　quantitative　analysis　of　the　failure.　For　the　key　links　resulting　in　the　failure,some　countermeasures　are　presented.