The synthesis of vinyl acetate (VAc) from ethylene is a strongly exothermic reaction that might easily cause catalyst deactivation and reduce selectivity of VAc. Research at the bed scale helps to improve the conversion of C2H4 and the selectivity of VAc. In this study, the discrete element method (DEM) was used to construct a fixed-bed structure model via simulating the filling process of catalyst particles in the reactor. The inlet section of a reaction tube was studied, and its length was 10 cm. The temperature distribution, and the effects of particles size, inlet velocity, inlet temperature and the feed ratio of C2H4 to O2 on the reaction process were studied. Simulated results show that the bed temperature gradually increased from the wall to the center, and the temperature gradient gradually decreased along the radial direction. The maximum temperature was 438.68 K and the temperature difference from the inlet temperature was 5.54 K. Comparing the composite particle packed bed with the single particle size packed bed, the composite packed bed has higher vinyl acetate selectivity. Increasing inlet velocity from 1.5m/s to 3.5m/s, the selectivity of vinyl acetate increased from 91.71% to 92.60%. Adding an inert gas to the feed gas can increase the oxygen concentration and reduce the explosion interval of C2H4, the conversion of C2H4 and the selectivity of vinyl acetate increased.