Preparation　of　the　second-generation　high-temperature　superconducting　tape　by　ion　beam-assisted　deposition　(IBAD)　requires　a　flat　metal　substrate.　In　this　work,　the　electrochemical　polishing　of　long-length　Hastelloy　C-276　alloy　was　studied,　and　its　process　parameters,　characterized　roughness　and　other　properties　were　investigated.　A　10-meter-long　Hastelloy　C-276　alloy　was　prepared　by　electrochemical　polishing.　The　following　optimized　processing　parameters　are　obtained:　temperature　of　45　A　degrees　C,　current　density　of　0.439　A　center　dot　cm(-2)　and　polishing　time　of　60　s.　The　average　roughness　value　(R　(a))　of　the　surface　is　less　than　5　nm　(5　mu　m　x　5　mu　m),　which　was　characterized　by　atomic　force　microscopy.　This　value　satisfies　the　requirements　for　the　further　preparation　of　transition-layer　pair　by　the　IBAD　technology　route.