Against the backdrop of rapid advances in digital and intelligent technologies and the deepening implementation of the Chinese path to modernization, understanding modern infrastructure and the construction of its system from a systemic perspective has become a key issue for high-quality socio-economic development and the modernization of national governance. This study conceptualizes modern infrastructure as a comprehensive technological-institutional system formed through the integration of physical entities, cognitive intelligence, and institutional rules. Through technological supply, scenario responsiveness, and rule embedding, modern infrastructure continuously expands its capacity to support innovation and governance. It exhibits four intrinsic characteristics: system-wide perception enabled by digital-physical isomorphism, model-driven cognitive iteration, resilient self-adaptation enabled by endogenous regulation, and scenario-driven ecosystem co-creation. Building on a collaborative evolution model of "forward driving‒reverse guidance‒lateral regulation", this study elucidates three mechanisms governing the interaction between modern infrastructure and socio-economic systems: the value-creation mechanism from factor support to the incubation of new quality productive forces, the intelligent iteration mechanism from passive use to demand-driven redefinition, and the institutional governance mechanism from external constraint to resilient adaptation. At the system level, it proposes a construction pathway in which strategic orientation clarifies development priorities, structural optimization strengthens network coordination, mechanism innovation ensures stable operation, and feedback calibration enhances system adaptability. The study can provide a reference for deepening the theoretical understanding of modern infrastructure and advancing the coordinated construction of a modern infrastructure system.