Abstract: Changing the pre-exponential factor and the activation energy coefficient, the single-step reaction mechanism for hydrogen combustion was established, and the calculation and analysis of hydrogen combustion have been conducted by this mechanism. The results from the calculation and the experiment were compared, and the calculations of hydrogen combustion were processed in different hydrogen concentration by the single-step reaction mechanism. The results showed that the calculations and experimental flame propagation were conformable, and the modified single-step reaction mechanism for hydrogen combustion can be used to calculate and analyze the hydrogen combustion in nuclear power plants.