Abstract: Solid oxide electrolysis cell (SOEC) technology offers advantages such as high efficiency and reversible operation, but its scale-up is constrained by the limited power rating of individual stacks, high-temperature operation, and consistency issues among multiple stacks. This paper reviews the progress in SOEC system integration and engineering scale-up. Planar, tubular, and flat-tubular configurations and their stacking approaches are compared, and key issues in stack scale-up, including material and interface compatibility, electro-thermal-flow field uniformity, and mechanical reliability, are analyzed. Multi-stack modular integration, thermal management, balance-of-plant (BOP) configuration, and integration with external heat sources are summarized, together with key enabling technologies such as online diagnostics, balancing control, and lifetime management. The analysis indicates that multi-stack modularization and efficient thermal integration are the principal engineering pathways toward large-scale SOEC systems, while multi-stack operational consistency, the reliability of high-temperature BOP components, and long-term lifetime management remain critical challenges for further scale-up.