Ruthenium-Cobalt photocatalytic system (RCPS) is one of the most prominent candidates for integrating homocatalysis and heterocatalysis, which has recently attracted extensive research attention for photocatalytic CO2 reduction reaction (PCO2RR). In RCPS, the coordination environment of the catalytic site and the efficiency of electron transfer can determine the reaction pathways in PCO2RR and hence, which is importance of evaluating and guiding PCO2RR. We aim to provide the first systematic review of RCPS in CO2 reduction, describing recent progress on the coordination effect of Ru-Co in homogeneous and heterogeneous photocatalysis systems. Specifically, we try to reveal the relationship between homogeneous and heterogeneous CO2 reduction systems on the reactivity and electron transfer. In addition, the advanced characterization techniques, the challenges for first-principal density functional theory, future challenges and perspectives for RCPS research are provided in this comprehensive review.