Fe3N　nanocrystals　embedded　in　cracked　N-doped　carbon　nanotubes　(Fe3N@NCNT)　with　a　cowpea-like　shape　are　innovatively　prepared　by　metal-catalyzed　graphitization　and　nitridization　processes　based　on　melamine　and　FeC2O4　precursor.　The　new　in-situ　synthesis　strategy　is　proved　to　be　effective　to　open　the　NCNT　using　a　migratory　metal　carbide　nanocatalyst　via　expansion　effect　and　fabricate　a　metal　nitride　embedded　NCNT　with　fully　active　ingredients.　The　detailed　tip-growth　mechanism　of　cracked　NCNT　with　latitudinal-longitudinal　graphene　layers　is　studied　by　in-situ　XRD　analysis　of　the　phase　evolution　of　melamine　and　FeC2O4,　and　ex-situ　SEM/TEM　investigation　of　the　topography　correlation　of　NCNT　and　Fe3C　floating　catalyst.　The　Fe3N@NCNT　microclews　based　anodes　have　a　moderate　carbon　content　of　35.45　wt%,　electroactive　NCNT　conductive　network,　abundant　microcracks　and　an　open　short-cavity　system,　showing　a　stable　discharge　capacity　of　667　mAh　g-1　at　0.1C,　outstanding　rate　capability　of　448　mAh　g-1　at　5C　and　remarkable　long-term　cycling　stability　of　546　mAh　g-1　after　600　cycles　at　1C.　The　combined　good　electronic/ionic　conductivity　of　cracked　NCNT　and　robust　mechanical　stability　of　geometrically　confined　Fe3N　nanoparticles　contribute　to　the　excellent　redox　activities,　stabilized　solid-electrolyte-interphase　film　and　cycling　durability　of　Fe3N@NCNT.