The　energy　during　the　process　of　self-diffusion　in　BCC　transition　metals　Fe,　W,　Mo,　Cr,　Ta,　Nb　and　V　has　been　calculated　by　using　modified　analytic　embedded-atom　method　(MAEAM).　For　each　kind　of　three　diffusion　mechanisms　nearest-neighbor　(NN),　nextnearest-neighbor　(NNN)　and　third-nearest-neighbor　(TNN),　the　energy　curve　is　symmetric　and　the　maximum　value　of　the　energy　appears　at　the　middle　point　of　the　diffusion　path.　Determined　mono-vacancy　formation　energy　E-1v(f),　migration　energy　E-1v(m)　and　activation　energy　Q(1v)　for　self-diffusion　agree　well　with　available　experimental　data　of　NN　diffusion　and　are　better　than　those　obtained　by　the　analytic　embedded-atom　method　(AEAM)　and　Finnis-Sinclair　models.　Compared　the　energies　corresponding　to　three　diffusion　mechanisms,　the　NN　diffusion　needs　the　lowest　activation　energy　(and　thus　the　lowest　migration　energy).　So　that,　the　NN　mono-vacancy　diffusion　is　favorable　in　BCC　transition　metals.　(c)　2006　Elsevier　B.V.　All　rights　reserved.