Efficient chemical transformation in a green, low-carbon way is crucial for the sustainable development of modern society. Enzyme-photo-coupled catalytic systems (EPCS) that integrate the exceptional selectivity of enzyme catalysis and the unique reactivity of photocatalysis hold great promise in solar-driven 'molecular editing'. However, the involvement of multiple components and catalytic processes challenged the design of efficient and stable EPCS. To show a clear picture of the complex catalytic system, in this review, we analyze EPCS from the perspective of system engineering. First, we disintegrate the complex system into four elementary components, and reorganize these components into biocatalytic and photocatalytic ensembles (BE and PE). By resolving current accessible systems, we identify that connectivity and compatibility between BE and PE are two crucial factors that govern the performance of EPCS. Then, we discuss the origin of undesirable connectivity and low compatibility, and deduce the possible solutions. Based on these understandings, we propose the designing principles of EPCS. Lastly, we provide a future perspective of EPCS.