In　this　paper,　the　magnetic　reversal　process,　hysteresis　loops　and　energy　products　for　exchange-coupled　Nd2Fe14B/alpha-Fe　bilayers　are　studied　systematically　by　a　three-dimensional　(3D)　model.　The　3D　calculations　are　numerically　solved　using　the　finite　difference　method,　where　the　results　are　carefully　compared　with　those　calculated　by　one-dimensional　(1D)　model.　It　is　found　that　the　calculated　hysteresis　loops　and　energy　products　based　on　the　two　methods　are　consistent　with　each　other.　Both　nucleation　fields　and　coercivities　decrease　monotonically　as　the　soft　layer　thickness　L-s　increases.　In　addition,　the　calculated　spatial　distributions　of　magnetization　orientations　in　the　thickness　direction　at　various　applied　fields　based　on　both　methods　signify　a　three-step　magnetic　reversal　process,　which　are　nucleation,　growth　and　displacement　of　the　domain　wall.　The　calculated　magnetic　orientations　within　the　film　plane,　however,　are　totally　different　according　to　the　two　methods.　The　3D　calculation　exhibits　a　process　of　vortex　formation　and　annihilation.　On　the　other　hand,　the　1D　calculation　gives　a　quasi-coherent　one,　where　magnetization　orientation　is　coherent　in　the　film　plane　and　varies　in　the　thickness　direction.　This　new　reversal　mechanism　displayed　in　the　film　plane　has　a　systematic　influence　on　the　nucleation　fields,　coercivity　and　energy　products.　(C)　2013　Elsevier　B.V.　All　rights　reserved.