The utilization of in-situ resource on Mars is currently one of the key research focuses in deep space exploration. Non-thermal plasma technology provides a promising approach for in-situ conversion of high-concentration CO₂ in the Martian atmosphere, with advantages such as strong environmental adaptability and high system efficiency. In this study, a coaxial packed-bed dielectric barrier discharge reactor is employed to investigate the discharge characteristics of simulated Martian atmospheric CO₂, with particular emphasis on the effects of SiO₂ and Al₂O₃ packing materials on CO₂ conversion performance and energy consumption. Through in-situ spectral diagnostics, the variation patterns of characteristic spectral lines of excited-state CO₂ and O₂ under different operating conditions are investigated in this work. It is found that increasing the discharge power promotes the generation of excited-state reactive species, which facilitates the activation and conversion of carbon dioxide. Furthermore, increasing the discharge power effectively enhances the electric field strength in CO₂ discharge. Compared with plasma only and the use of SiO₂ packing material, the system exhibits a more significant electric field enhancement effect when packed with Al₂O₃ beads. Based on numerical simulations, the electron impact reaction rate constant and electron energy distribution function of CO₂ discharge are obtained. The results reveal that packing the discharge gap with Al₂O₃ material significantly changes the physical characteristics of CO₂ discharge, enhances both the electric field strength and the mean electron energy, thereby generating more high-energy electrons and asymmetric vibrational excited states of CO₂. This ultimately promotes the CO₂ decomposition reaction for oxygen production. Finally, the study examines the effectiveness of CO₂ decomposition for oxygen production under various typical operating conditions. It is demonstrated that increasing the discharge power and packing with Al₂O₃ both contribute to improving the CO₂ conversion rate and oxygen production rate, while reducing the energy consumption of the reaction. The introduction of Al₂O₃ packing enhances the electric field strength, thereby improving CO₂ conversion and O₂ production, achieving a CO₂ conversion rate of 12.18% and a minimum energy consumption of 0.36 kWh/g. This study provides theoretical and experimental support for the future applications of non-thermal plasma technology in the in-situ resource utilization of Martian atmosphere, offering insights into sustainable resource utilization in deep space exploration.