To　safely　and　reliably　use　nanowires　(NWs)　for　exploring　new　functions　for　different　nanodevices,　the　mechanical　properties　and　structural　evolution　of　the　nanowires　under　external　stress　become　highly　important.　Large　strain　(up　to　14%)　bending　experiments　of　Si　NWs　were　conducted　in　a　high-resolution　transmission　electron　microscope　at　atomic　resolution.　The　direct　dynamic　atomic-scale　observations　revealed　that　partial　and　full　dislocation　nucleation,　motion,　escape,　and　interaction　were　responsible　for　absorbing　the　ultralarge　strain　of　up　to　14%　in　bent　Si　nanowires.　The　prevalent　full　dislocation　movement　and　interactions　induced　the　formation　of　Lomer　lock　dislocations　in　the　Si　NWs.　Finally,　in　contrast　to　the　unlock　process　of　Lomer　dislocations　that　can　happen　in　metallic　materials,　we　revealed　that　the　continuous　straining　on　the　Lomer　dislocations　induced　a　crystal-amorphous　(c-a)　transition　in　Si　NWs.　Our　results　provide　direct　explanation　about　the　ultralarge　straining　ability　of　Si　at　the　nanometer　scale.