Hysteresis effects and reaction characteristics of methane catalytic partial oxidation (CPO) in a fixed-bed reactor are numerically simulated. The reactions are modeled based on the experimental measurements of methane CPO with a rhodium (Rh) catalyst. Three C/O ratios of 0.6, 1.0 and 1.4 are considered in the study. When the Reynolds number is 200, the predictions indicate that the methane CPO is always triggered at around the inlet temperature of 550 K, regardless of what the C/O ratio is. It is of interest that if the inlet temperature is decreased after the methane CPO develops at higher inlet temperatures, the reversed path of methane conversion is different from the original path at lower inlet temperatures. The hysteresis effect of the methane CPO is thus observed. The hysteresis behavior implies that a higher yield of syngas or hydrogen can be achieved by controlling the reaction process. Decreasing the C/O ratio intensifies the methane CPO so that the hysteresis effect is more pronounced, and vice versa. An increase in Reynolds number delays the excitation temperature of methane CPO and lessens the hysteresis effect of methane conversion due to the growth of fluid inertial force. However, the hysteresis effect of the maximum temperature in the catalyst bed increases as a result of more methane consumption. (C) 2009 Elsevier B.V. All rights reserved.