Abstract: Taking the volatile organic compounds （VOCs） catalytic combustion reactor of a certain enameled wire enterprise as the research object， Fluent software was used to conduct numerical simulation of its internal flow field. The effects of inlet expansion section length， inlet expansion section angle， and catalyst bed spacing on the velocity field within the reactor were investigated. Additionally， the changes in the reactor's temperature field following alterations to the heating tube configuration were analyzed. The results demonstrated that， considering the actual effective space and influencing factors such as the formation of flow recirculation zones， an expansion section length of 250 mm was deemed appropriate. The most homogeneous axial gas velocity distribution within the reactor was achieved when the expansion section angle was 0°； however， the expansion section angle should be selected according to specific operating conditions. A catalyst bed spacing of 0.05 m not only satisfied the engineering requirement of maintaining the pressure drop across a single catalyst layer at or below 200 Pa but also significantly improved gas flow distribution within the catalyst bed. The gas temperature distribution was found to be most favorable in the region with alternating heating tubes on both sides， as this configuration facilitated an overall temperature rise of the catalyst bed， thereby promoting the catalytic combustion process of VOCs.