Solid-state lithium batteries with expected high energy density, wide operating temperature range, and high safety will become the primary choice in the field of power supply and energy storage. However, issues like high ion/electron migration resistance, insufficient stability, and ease of peeling at the solid-solid interface considerably limit their practical applications and industrialization. A deep understanding of the ion/electron conduction mechanism is imperative for improving the performance of solid-state batteries. Regarding this, it is necessary not only to obtain original experimental data but also to analyze the mutual influence of ions/electrons and their independent contribution to the total polarization loss through transmission line models. The following aspects are discussed in this brief review: (1) the seven experimental methods for measuring ion/electron conductions in porous electrodes and their characteristics are reviewed; (2) ion/electron conductions in porous electrodes and their nine transport line models are discussed; (3) the unsolved problems in the study of ion/electron conduction mechanism are analyzed; (4) the possible directions of efforts to improve the cycle stability of solid-state batteries are proposed. This review benefits readers by quickly elucidating the research status, key issues, and development trends of ion/electron conduction in intercalation electrodes.