Supercritical　water　fluidized　bed　(SCWFB)　is　a　promising　reactor　to　gasify　biomass　or　coal.　Its　optimization　design　is　closely　related　to　wall-to-bed　heat　transfer,　where　particle　convective　heat　transfer　plays　an　important　role.　This　paper　evaluates　the　particle　convective　heat　transfer　coefficient　(hpc)　at　the　wall　in　SCWFB　using　the　single　particle　model.　The　critical　parameters　in　the　single　particle　model　which　is　difficult　to　get　experimentally　are　obtained　by　the　computational　fluid　dynamics-discrete　element　method　(CFD-DEM).　The　contact　statistics　related　to　particle-to-wall　heat　transfer,　such　as　contact　number　and　contact　distance,　are　also　presented.　The　results　show　that　particle　residence　time　(T),　as　the　key　parameter　to　evaluate　hpc,　is　found　to　decrease　with　rising　velocity,　while　increase　with　larger　thermal　boundary　layer　thickness.　T　follows　a　gamma　function　initially　adopted　in　the　gas-solid　fluidized　bed,　making　it　possible　to　evaluate　hpc　in　SCWFB　by　a　simplified　single　particle　model.　The　theoretical　predicted　hpc　tends　to　increase　with　rising　thermal　gradient　thickness　at　a　lower　velocity　(1.5　Umf),　while　first　decreases　and　then　increases　at　higher　velocity　(1.75　and　2　Umf).　hpc　occupies　30%-57%　of　the　overall　wall-to-bed　heat　transfer　coefficient　for　a　particle　diameter　of　0.25　mm.　The　results　are　helpful　to　predict　the　overall　wall-to-bed　heat　transfer　coefficient　in　SCWFB　combined　with　a　reasonable　fluid　convective　heat　transfer　model　from　a　theoretical　perspective.　(c)　2022　Published　by　Elsevier　B.V.　on　behalf　of　Chinese　Society　of　Particuology　and　Institute　of　Process　Engineering,　Chinese　Academy　of　Sciences.