This　paper　presents　an　investigation　of　the　flow　and　heat　transfer　characteristics　of　the　water　wall　tube　of　an　ultra-supercritical　circulating　fluidized　bed　(CFB)　boiler　for　a　better　boiler　design.　The　operating　pressure　ranges　from　10.5　to　32　MPa.　The　six-headed　inner　rifled　tube　used　in　the　test　has　a　diameter　and　wall　thickness　of　35　mm　and　5.67　mm,　respectively.　Results　show　that　the　vapor　quality　during　heat-transfer　deterioration　(vapor　quality　＞　0.8)　increases　with　increased　mass　flux　or　decreased　heat　flux　in　the　subcritical　pressure　regions.　The　effects　of　the　pressure　and　heat　flux　on　the　inner-wall　temperature　in　the　supercritical　pressure　region　are　remarkable　in　the　high-enthalpy　region　(enthalpy　＞　2400　kJ　kg(-1)).　The　effects　of　the　heat　flux　and　pressure　on　frictional　pressure　drop　are　more　dominant　than　mass　flux　in　both　the　subcritical　and　supercritical　pressure　regions.　The　optimized　tube　is　found　to　exhibit　good　performance　under　ultra-supercritical　parameters.