Abstract: Based on the LHS (Latin hypercube sampling) method, Pearson and Spearman correlation coefficients, the uncertainty quantification of hydrogen source term and parameter importance analysis under the severe accident (SA) of station black out (SBO) were performed for the 600 MW nuclear power plant through MELCOR code. The thermal power of the plant, the porosity of the debris bed, the temperature to which oxidized fuel rods can stand in the absence of unoxidized Zr in the cladding and the maximum melt flow rate after breakthrough were selected as uncertain input variables. The statistical distribution of hydrogen production in-vessel with 95% confidence and the influence degree of each parameter were obtained through the calculation of 100 sets of input. The results show that the hydrogen production in-vessel is in the range of 239 kg to 424 kg, which is equivalent to the hydrogen generated from the 34.5% to 61.2% of the zirconium-water reaction and conforms to the normal distribution, and the porosity of the debris bed has a significant positive correlation with hydrogen production.