Abstract: Criticality safety analysis for AP1000 spent fuel storage racks (SFSRs) employing burnup credit was recalculated based on SCALE6 code package. Combined with the design characteristics of AP1000 core reactivity control, the effect of axial burnup distribution on system reactivity was analyzed. The results show that the system reactivity is more conservative at high burnup using MSHIM axial burnup distribution, and the effect of neutron absorbers exposure on the reactivity of assembly during depletion should be considered in criticality safety analysis, and soluble boron should not be credited.