Abstract: The method of statistical analysis for the reliability of nuclear power units was proposed, and the meaning and computational formula for five reliability characteristic quantities of nuclear power units were introduced. The weighted arithmetic means of reliability characteristic quantities of nuclear power units were presented, while following items of 1 000 MW class nuclear power units in China and America from 2008 to 2022 were given, namely the statistic results of reliability, the calculation results of weighted arithmetic means of reliability characteristic quantities, and the change curves of reliability characteristic quantities. Results show that, for 1 000 MW class nuclear power units in China, the availability, reliability and maintainability in general, all present a trend of increase, while the equivalent availability factor of 1 000 MW class nuclear power units from 2008 to 2022 in China is 1.81 percentage points higher than that in America.