Abstract: Underground substations in low-lying areas are prone to water ingress, difficult drainage, and severe regional power outages from flooding. Therefore, flood prevention measures must be reliable. This paper briefly analyzes the flood prevention characteristics of underground substations, systematically summarizes the achievements gained from recent technological advancements and practical experience, and summarizes a comprehensive "four-in-one" flood prevention system for underground substations covering early warning monitoring, external water blocking, internal drainage, and emergency reinforcement. This system can guide relevant flood prevention work and ensure the safe and stable operation of substations during the flood season.