Abstract: Mathematical simulation was performed on a tube-shell type fixed-bed reactor for dimethyl ether (DME) synthesis. Hydrogenation of CO and CO_2 and dehydration of methanol to dimethyl ether were selected as independent reactions, CO, CO_2 and DME as key components to establish the one-dimensional mathematical model of the reactor. The gas concentration and temperature profiles inside the reactor tubes were obtained. The operating conditions affecting DME synthesis were discussed based on the model. The simulation results show that hotspot temperature of catalyst bed, CO conversion and production of methanol and DME rise markedly with the increase of operating pressure, while with the increase of the (inlet) gas flow rate, hotspot temperature and CO conversion drop, but the production increases.