©　2016,　Editorial　Department　of　＂Journal　of　Engineering　for　Thermal　Energy　and　Power＂.　All　right　reserved.　The　water　wall　system　can　be　equivalent　to　a　boiler　network　consisting　of　pressure　nodes　and　connecting　pipe　groups,　considering　the　structure　feature　of　ultra-supercritical　double　reheat　once-through　boiler.　A　mathematical　model　for　calculating　pressure　drop,　mass　flow　rate,　and　steam　temperature　was　established　on　the　basis　of　the　mass,　momentum,　and　energy　conservation　laws.　Moreover,　the　thermal　hydrodynamic　performance　of　a　1　000　MW　supercritical　double　reheat　once-through　boiler　with　spiral　tube　coils　at　Taizhou　Power　Plant　was　studied　under　different　loads.　The　results　show　that　the　mass　flow　rate　of　lower-furnace　has　an　uniform　distribution,　the　mass　flow　rate　of　upper-furnace　presents　the　positive　flow　response　characteristics,　the　steam　temperature　undergoes　the　endothermic　flat　area,　and　the　outlet　steam　temperature　in　middle　wall　of　different　furnaces　is　the　highest.