This study presents a novel microscopic bubble/precipitate traffic system (MBPTS) that enables stable seawater reduction electrocatalysis at industrial-level current densities. The MBPTS is integrated into a honeycomb-like 3D cathode structure, which efficiently releases small-sized H₂ bubbles to repel Mg²⁺/Ca²⁺ precipitates. The optimal cathode with built-in MBPTS achieves state-of-the-art alkaline seawater reduction (SR) performance, operating stably for 1000 hours at -1 A cm⁻² and demonstrating high catalytic efficiency in splitting natural seawater into H₂ with strong anti-precipitation ability. A flow-type electrolyzer based on this cathode functions stably at 500 mA cm⁻² for 150 hours in natural seawater, maintaining near-100% H₂ Faradic efficiency. The estimated price of H₂ production is even cheaper than the US Department of Energy's goal price. The study highlights the importance of cathode performance in seawater splitting, particularly in natural seawater, and demonstrates the effectiveness of the MBPTS in preventing precipitation and enhancing electrocatalytic activity. The NCP/PC cathode exhibits exceptional performance, with a low Tafel slope, high double-layer capacitance, and excellent stability under industrial-level current densities. The MBPTS enables efficient bubble transport and precipitation removal, leading to superior eASR and eNSR performance. The study also demonstrates the practical application of the NCP/PC cathode in a flow-type electrolyzer, achieving long-term stability and high H₂ production efficiency. The results highlight the potential of the MBPTS in advancing seawater electrolysis for sustainable hydrogen production.This study presents a novel microscopic bubble/precipitate traffic system (MBPTS) that enables stable seawater reduction electrocatalysis at industrial-level current densities. The MBPTS is integrated into a honeycomb-like 3D cathode structure, which efficiently releases small-sized H₂ bubbles to repel Mg²⁺/Ca²⁺ precipitates. The optimal cathode with built-in MBPTS achieves state-of-the-art alkaline seawater reduction (SR) performance, operating stably for 1000 hours at -1 A cm⁻² and demonstrating high catalytic efficiency in splitting natural seawater into H₂ with strong anti-precipitation ability. A flow-type electrolyzer based on this cathode functions stably at 500 mA cm⁻² for 150 hours in natural seawater, maintaining near-100% H₂ Faradic efficiency. The estimated price of H₂ production is even cheaper than the US Department of Energy's goal price. The study highlights the importance of cathode performance in seawater splitting, particularly in natural seawater, and demonstrates the effectiveness of the MBPTS in preventing precipitation and enhancing electrocatalytic activity. The NCP/PC cathode exhibits exceptional performance, with a low Tafel slope, high double-layer capacitance, and excellent stability under industrial-level current densities. The MBPTS enables efficient bubble transport and precipitation removal, leading to superior eASR and eNSR performance. The study also demonstrates the practical application of the NCP/PC cathode in a flow-type electrolyzer, achieving long-term stability and high H₂ production efficiency. The results highlight the potential of the MBPTS in advancing seawater electrolysis for sustainable hydrogen production.