Three-dimensional models were set up for the oxidative coupling of methane (OCM) two-stage packed bed reactors loaded with Na2WO4-Mn/SiO2 particle catalyst and Na3PO4-Mn/SiO2/cordierite monolithic catalyst using the computational fluid dynamics simulation. Firstly, the reactor with particle and monolithic catalyst bed heights of 10 mm and 50 mm was simulated. Secondly, the effects of particle and monolithic catalyst bed heights on reactor performance were investigated. The results showed that the simulation values matched well with the experimental values on the conversion of CH4 and the selectivity of products (C2H6, C2H4, CO, CO2) in the reactor outlet with an error range of +/- 10%. The monolithic catalyst bed had a higher C-2 (C2H4 and C2H6) selectivity and less O-2 consumed than the particle catalyst bed did. When the heights of particle and monolithic catalyst bed were 10 mm and 50 mm, respectively, the best values of C-2 yield were 21.8% obtained due to the effects of residence time and the CO2 blocking in the oxidation reaction. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.