The effects of various factors on the mechanical strength of iron-based high temperature water-gas shift catalyst in calcination processes has been investigated in detail by a set of second order optimum experiments. Due to one of these factors, the moisture content could not be optimized in the range examined, and the optimum values of the factors were not found by this set of experiments. Nevertheless, the experimental results and the analysis of the data give much indication on the mechanical properties of the catalyst. The calcination temperature, the heating rate, the moisture content and the calcination time respectively, all have strong effects on the resulting strength of the catalyst. The statistics of the data show that the scattering behaviour of the horizontal crushing strength of the catalyst pellet can be described by Weibull distribution. The reliability of the strength is related mainly to the value of the Weibull modulus. The results show that it is possible to reduce the probability of strength failure at low density, and that there exists much possibility to increase the reliability of strength. It has been reported that one of the samples has a Weibull modulus as high as 17.1 and a probability of failure at 10 kg/pellet as low as 6.56 x 10(-13). The value of this probability is 9 orders of magnitude lower than that of the best commercial sample at the same stress condition.