Abstract: The electrocatalytic CO₂ reduction reaction （eCO₂RR） technology is promising due to its mild and controllable reaction conditions, and its compatibility with renewable energy sources. In particular, membrane electrode assembly （MEA） electrolytic cells, with their compact structure, high energy efficiency and low ohmic losses, have the potential for industrial applications. However, current numerical modeling studies of eCO₂RR often overlook the influence of acid-base equilibrium reactions in solution on the electrochemical process, and lack performance. By geometrically modeling the MEA electrolytic cell, establishing and coupling the flow field, in-depth exploration of the role of gas diffusion layer （GDL） thickness and catalyst layer （CL） porosity on the system electrochemical reaction, acid-base equilibrium reaction, concentration field and other multi-physical fields, a dynamic and comprehensive model of a two-dimensional MEA electrolytic cell was successfully built. This model was utilized to explore the effects of the inhomogeneous distribution phenomenon of chemical reactions in the electrolytic cell, the thickness of the GDL, and the CL porosity on the MEA electrolytic cell system. Simulation indicate that unbalanced acid-base reactions cause localized pH fluctuations in the cathode region, altering the local chemical environment and leading to an inhomogeneous current density distribution along the flow path in CL. Furthermore, variations in GDL thickness and CL porosity significantly influence gas transport and electrode reaction, changing the feedstock distribution, products distribution and product yields. As the GDL thickness increased from 100 μm to 400 μm, the total CO production increased from 7.01×10⁻¹⁴ mol to 7.62×10⁻¹⁴ mol, but the proportion in the cathode flow channel decreased significantly, which was unfavourable for product collection. When the GDL thickness was greater than 350 μm, the CO content in the flow channel showed a decreasing trend. As the CL porosity increased from 0.3 to 0.8, the CO yield in the CL increased to nearly triple, but the enhancement of the hydrogen precipitation reaction was detrimental to the product selectivity. The proposed two-dimensional dynamic MEA model and the insights into the performance of eCO₂RR offer valuable contributions to the design and development of future electrolyzers.