Interfacial　bonding　reliability　is　a　critical　issue　in　bimetallic　structures.　To　understand　the　effect　of　deposition　sequence　on　interfacial　characteristics,　bimetallic　structures　of　Inconel　and　copper　alloys　were　fabricated　by　directed　energy　deposition　arc　(DED-Arc).　The　interfacial　element　diffusion　behaviors　and　formation　mechanisms　were　investigated　in　detail.　The　bimetallic　structure　of　C18150　on　GH4169　exhibits　a　sound　metallurgical　bonding　interface　with　a　wide　interfacial　region　(similar　to　400　mu　m),　which　is　attributed　to　Marangoni　convection　and　intense　elemental　interdiffusion.　The　study　highlights　the　feasibility　of　fabricating　large　Inconel-copper　functional　bimetallic　structures　with　sound　metallurgical　bonding　using　DED-Arc　and　it　provides　a　theoretical　reference　for　design　and　fabrication　of　bimetallic　structures　with　material-property　mismatches.