<p>Defect engineering provides a promising strategy to design efficient photo-thermal catalysts for methane dry reforming reaction, addressing challenges of harsh reaction conditions, and ultimately achieve the reduction of carbon footprint. Here, a series of Ru-Ceria catalysts with different defect structures were synthesized by controlling the duration of hydrothermal self-assembly treatment, and their physicochemical properties were systematically characterized. The results revealed how the sensitivity of the surface defect engineering affected the optical and catalytic performance of the catalysts. Furthermore, by integrating the operando characterization and structural analysis, a linear correlation between structure (Defects concentration, Ru⁰ content), intermediate species (CO^* and CH_x^* species) and catalytic performance (Products formation rates and catalytic stability) was established. This work provided a theoretical foundation for the application of surface defect engineering in photothermal MDR catalysis.</p>