The　deformation　and　structure　stability　of　graphite　cathodes　are　of　importance　for　its　service　lifetime.　The　time　dependence　and　coupling　of　deformation,　elastoplastic　property　change　and　microstructure　evolution　of　graphite　cathodes　were　investigated　under　constant　pressure　at　940　degrees　C.　The　deformations　from　early　expansion　transiting　to　the　rapid　and　latter　steady　creep　were　found　with　increased　hardness　and　modulus,　in　parallel　with　decreasing　interplanar　spacing　of　graphite　(002)　planes　(d(002))　and　increasing　crystallite　size　along　c-axis　of　graphite　lattice　(L-c).　The　inner　fracture　among　(002)　planes　may　be　related　to　the　kink　bands　structure　in　graphite.　It　is　clarified　that　no　Na-C　intercalation　compounds　get　involved　in　change　of　graphite　lattice.　The　crystallite　size　along　a-axis　(L-a)　can　play　an　important　role　in　structure　stability　with　deformation-hardening　effect　on　elastoplastic　property　and　pinning　effect　on　creep　resistance.　The　deformation　mechanism　and　the　influencing　factors　on　long-term　structure　stability　of　graphite　cathode　are　also　discussed　in　detail.