Abstract: CAP1400 is a new type of reactor developed independently in China, and the spent fuel storage racks stand freely in the spent fuel pool of CAP1400 reactor. Water can flow through the channels between the storage cells, while water is also found in the gap between the rack and rack, the rack and wall. In the case of earthquakes, due to the non-linearity of the fluid-structure interaction between the rack and water, it is difficult to calculate accurately with the software. In order to accurately investigate the characteristics of fluid-structure interaction, the experiment model of the spent fuel storage racks and the tank was established. The friction coefficient between the racks and the tank was measured by sweeping frequency test. At the same time, the influence of the gap size between the rack and rack on the sliding phenomenon and the fluid pressure was studied. The friction coefficient between the rack and the tank was obtained by analyzing the test results. Moreover, the larger the gap between the rack and rack is, the smaller the fluid pressure is, but the gap size has no obvious effect on the sliding phenomenon. The results can provide reference for design of CAP1400 spent fuel storage rack.