Abstract: Spent fuel storage racks stand freely in the spent fuel pool. There are certain gaps between the wall and rack. Under earthquake, fluid in these gaps dissipates racks’ energy by fluid-structure interaction, which ensures the structural integrity of the racks. According to the different rack storage cell designs of AP1000 and CAP1400, the sidewall of the rack may be flat plate or orifice plate. In structural dynamics analysis of rack, in order to simplify the calculation of added mass fluid gap, the orifice plate will be simplified to flat plate directly. Such approach does not accurately reflect the actual fluid-structure coupling effect. To study the rack-rack and wall-rack fluid-structure interaction effect, several vibration tests were set up, and fluid forces of orifice plate with different gaps and different excitation frequencies were measured. Fluid forces for orifice plate were obtained in the experiment. The added masses of orifice plate were also obtained, which can provide reference for design of AP1000 and CAP1400 series spent fuel rack.