Within the electrolysis cell, a series of complex physical and chemical reactions occur, which interact and constrain one another. To design a highly active catalytic reactor, it is crucial to have full cognition of the multi-scale material transport and reaction process inside the reactor. Based on computational fluid dynamics methods, this study builds a three dimensional model of the electrolysis cell, and develops a computational program for simulating the carbon dioxide electrocatalytic reduction process. Additionally, a carbon dioxide electrolysis conversion test system is designed and constructed to perform performance tests under typical operating conditions. The reliability of numerical results is verified by comparison with experimental results. The current density is found higher in regions under the rib than that under the channel, especially in the area where the channel and the diffusion layer intersects. The increase in temperature resulted in a decrease in current density, while a decrease in porosity leads to an increase in current density, which is primarily caused by changes in the reaction rate of the carbon dioxide conversion reaction.