Abstract: Based on the burn-up credit method, the effect of the soluble boron concentration in the storage on k_eff was studied by APOLLO and MCNP5 program. The results showed that the change rate of k_eff resulted from the change of the concentration of soluble boron in the storage reduced with the increasing of the fuel enrichment, approximately in linear. Mutual interference effects of the neutron poison in the storage were the main contribution to the absorber value. The neutron poison value has a liner relationship with the distance of the BSS plate. The improved layout scheme of neutron poison in accordance with the energy spectrum distribution of neutron outside the spent fuel assemblies can improve the critical security and economy of the spent fuel storage systems.