The　metastable　bcc-Cu　precipitation　behavior,　with　particular　focus　on　effect　of　metastable　bcc-Cu　on　microstructural　evolution　and　strengthening　is　investigated　by　experiment　and　calculation　simulation　in　an　as-cast　Fe-B　alloy　containing　3　wt%　Cu　content.　The　results　show　that　the　metastable　bcc-Cu　precipitates　with　the　size　of　3　to　5　nm　can　precipitate　from　the　alpha-Fe　(pearlite).　During　the　precipitation　process,　the　metastable　bcc-Cu　can　act　as　the　highly　effective　heterogeneous　nuclei　of　pearlitic　ferrite,　which　results　in　the　formation　of　abnormal　pearlite.　Additionally,　the　existence　ofbcc-Cu　will　lead　to　the　refinement　of　abnormal　pearlitie,　the　dissolution　of　abnormal　pearlitic　cementite,　and　the　strengthening　of　pearlite.　The　microstructural　evolution　process　can　be　essentially　described　as:　L　(liquid　phase)　-＞　gamma　austenite),　L　-＞　gamma　+　M2B(boride),　gamma　-＞　P(normal　pearlite),　gamma　-＞　P　+　bcc-Cu-1　(the　first　precipitates),　gamma　-＞　P　+　P*(abnormal　pearlite)　+　bcc-Cu-2　(the　second　precipitates)　+　bcc-Cu-1,　and　gamma　-＞　M　(martensite).　Moreover,　the　calculation　simulation　analyses　are　in　good　agreement　with　the　experimental　results.