A　supercritical　water-fluidized　bed　(SCWFB)　is　a　very　promising　reactor　for　the　clean　utilization　of　biomass.　In　the　present　article,　the　flow　structure　in　SCWFB　is　analyzed　from　a　microscopic　point　of　view　via　a　special　measurement　system　based　on　a　capacitance　probe.　Five　groups　of　particles　are　fluidized　under　a　supercritical　condition　in　a　wide　range　of　operating　parameters:　20-27　MPa　and　410-570　degrees　C.　Fluctuations　and　distributions　of　local　voidage　are　analyzed　in　detail　to　shed　some　light　on　the　special　flow　structure.　The　results　show　that　bubbles　tend　to　move　toward　the　axial　line　of　SCWFB　and　slugging　fluidization　is　formed　at　a　higher　superficial　velocity.　In　particular,　a　Core-Annulus　Flow　in　SCWFB　is　found,　which　is　enhanced　by　the　increase　of　superficial　velocity　or　decrease　of　the　particle　diameter.　The　results　may　be　useful　for　the　development　of　the　SCWFB　technique.