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Accelerating urbanization and climate change have intensified urban flood risks, rendering underground spaces—critical hubs of modern infrastructure—inherently vulnerable to rapid inundation. Unlike surface flooding, underground inundation is characterized by the funneling effect and high-velocity inflows, often resulting in supercritical flows that cause catastrophic damage. Despite the widespread deployment of physical interventions such as flood barriers and watertight doors, a unified global standard for evaluating their performance remains absent. This study comprehensively reviews the mechanisms of underground flooding and critically analyzes the performance evaluation standards of nations: the USA (ANSI/FM 2510), the UK (BS 851188), Japan (JIS A 4716), and South Korea (KS F 2639).The comparative analysis reveals that while existing standards possess distinct strengths—ranging from comprehensive reliability verification (USA) and strict water exclusion targets (UK) to practical performance grading systems (Japan)—they predominantly rely on hydrostatic pressure testing. This static approach fails to adequately represent the hydro-complex dynamics of underground flooding, specifically the dynamic surge pressures and debris impacts generated at steep entrances. Furthermore, some regulations exhibit a regulatory lag, failing to reflect the actual hydrodynamic loads (e.g., velocities exceeding 3.0 m/s) or the advanced capabilities of modern technologies.To address these gaps, this paper proposes an integrated performance evaluation framework tailored to the unique risks of underground spaces. Key recommendations include: (1) a transition from static to Dynamic Hydro-Complex Load scenarios to simulate high-velocity surges; (2) the implementation of a Risk-Based Performance Grading System commensurate with facility criticality; and (3) the mandatory verification of lifecycle durability for equipment. This study provides a theoretical foundation for establishing international standards to enhance urban flood resilience.Keywords: Underground Flood; Flood Protection Equipment; Performance EvaluationAcknowledgements: This research was support by a (RS-2025-02218717) of Cooperative Research Method and Safety Management Technology in National Disaster funded by Ministry of Interior and Safety(MOIS, Korea).