The　mechanical　stability　of　metallic　nanomaterials　has　been　intensively　studied　due　to　their　unique　structures　and　promising　applications.　Although　extensive　investigations　have　been　carried　out　on　the　deformation　behaviors　of　metallic　nanomaterials,　the　atomic-scale　deformation　mechanism　of　metallic　nanomaterials　with　unconventional　hexagonal　structures　remains　unclear　because　of　the　lack　of　direct　experimental　observation.　Here,　we　conduct　an　atomic-resolution　in　situ　tensile-straining　transmission　electron　microscopy　investigation　on　the　deformation　mechanism　of　gold　nanoribbons　with　the　4H　(hexagonal)　phase.　Our　results　reveal　that　plastic　deformation　in　the　4H　gold　nanoribbons　comprises　three　stages,　in　which　both　full　and　partial　dislocations　are　involved.　At　the　early　deformation　stage,　plastic　deformation　is　governed　by　full　dislocation　activities.　Partial　dislocations　are　subsequently　activated　in　regions　that　have　undergone　full　dislocation　gliding,　leading　to　phase　transformation　from　the　4H　phase　to　the　face-centered　cubic　(FCC)　phase.　At　the　last　stage　of　the　deformation　process,　the　volume　fraction　of　the　FCC　phase　increases,　and　full　dislocation　activities　in　the　FCC　regions　also　play　an　important　role.