Abstract: The three-dimensional finite element model of AP1000 nuclear power plant core makeup tank (CMT) was established by using finite element software ANSYS in this paper. The structural characteristics of CMT were obtained by modal analysis, and the seismic response was simulated by time-history analysis which is more accurate. Through the mathematical model of seismic fragility of equipment, various fragility parameters of CMT were analyzed, and the median ground acceleration capacity A_m, the logarithmic standard deviations of the inherent randomness about the median β_R and the uncertainty in the median value β_U were gained by calculation of CMT fragility parameters. The high confidence and low failure probability (HCLPF) value was calculated. The results show that the HCLPF value of CMT is significantly higher than 0.3 g of the safe shutdown earthquake (SSE), which indicates that CMT has high seismic resistance, and the HCLPF value is slightly higher than that obtained by deterministic method. The sensitivity analysis of fragility parameter errors shows that the change of β_R has little influence on the conditional failure probability and HCLPF value of CMT. It can simplify the consideration of some randomness and make the fragility analysis more concise.