Abstract: The spray cooling experiment device was built based on beyond design basis event, and the electric heated rod bundle of 5×5 was used to simulate spent fuel assemblies. The purpose of this experiment is to research the minimum spray flow density which can maintain temperature of cladding in 300 ℃ and the influence to single-rod from around heated bundle when the water of spent fuel pool is completely lost. The spray experiment to spent fuel with low decay heat was carried out in the paper. The results show that heating bundles with the power less than 25 W are in safe condition without any cooling. The spray flow density of 2.393, 2.950 and 3.876 (m³/h)/m² can keep the temperature of heating bundles with the power of 100, 125 and 150 W in 300 ℃. The greatest impact comes from the first and the second floor bundles to the temperature of target rod and the third floor bundle and others have weak influence.