Heat　transfer　in　square　annular　upward　flow　channel　was　studied　on　the　supercritical　water　heat　transfer　facility　at　Xi＇an　Jiaotong　University.　Experimental　pressure　is　range　of　23-25　MPa,　mass　velocities　of　500-1200　kg/(m2·s),　heat　fluxes　of　200-800　kW/m2,　and　bulk　inlet　temperatures　of　300-400°C.　Experiment　results　showed　that　at　high　mass　velocity　and　relatively　low　heat　flux,　the　heat　transfer　in　square　annular　geometry　with　helical　wire-wrapped　spacer　would　be　enhanced,　whereas　at　low　mass　velocity　and　relatively　high　mass　flux,　the　heat　transfer　deterioration　would　occur.　Comparison　of　experiment　data　showed　that　at　lower　supercritical　pressure,　heat　transfer　was　enhanced　more　impressively　but　the　deterioration　was　more　likely　to　occur　while　relatively　higher　supercritical　pressure　means　better　security.