Abstract: The experiment was carried out to study the natural convection heat transfer of fuel assembly stayed in the transfer tube. The experiment data of the heating rods in the top corner of the carrier were obtained, and the correlations of heat transfer were proposed. The comparison between the calculated results and the experimental results show that the correlations can be used to calculate the local Nusselt number at the top corner of the heating rod. And it is varified that the heat transfer capacity of the No. 1 rod closest to the top corner of the carrier is the worst and the wall temperature is the highest under the same heat flux and inlet water temperature.