Abstract: Spent fuel storage rack is an important equipment for storing spent fuel assembly. Under seismic conditions, the response of rack is nonlinear and may cause slippage, subversion, etc., but fluid in these gaps dissipates racks’ energy by fluid structure interaction, which ensures the structural integrity of the rack. In this paper, 2D transient calculation on the 3/10 scale model of rack was conducted by using Fluent software. In the process of calculation, the dynamic mesh was used to simulate the forced vibration of the rack, and the parameter uncertainty was analyzed. By using CFD transient fluid force, the added mass matrices of double Ⅱ and double Ⅰ racks were obtained. Comparing the theoretical solution of the added mass with the analytical solution of the coaxial cylinder, the accuracy of the method in this paper was verified. The added mass matrices calculated in this paper can provide fluid structure interaction parameters for the dynamic software of spent fuel storage rack structure.