Abstract: The heat transfer experiment of supercritical water in two bundles with different P/D has been performed on the supercritical water multipurpose test loop coconstructed by China General Nuclear Power Corporation and Shanghai Jiao Tong University. The experiment data were obtained. The temperature non-uniformity in circumference of the bundles and heat transfer enhancement caused by the grids were observed obviously. The experiment research results of thermal-hydraulic parameters on heat transfer of supercritical water show that the heat transfer coefficient decreases and the temperature non-uniformity in circumference is enhanced with the increase of heat flux. The heat transfer coefficient increases and the temperature non-uniformity in circumference decreases with the increase of mass flux. The heat transfer coefficient decreases with the increase of system pressure. The heat transfer in bundles is enhanced with the decrease of P/D.