The photocatalytic purification reactor integrates TiO2 photocatalytic technology, high-speed microfilter filtration technology, electro-physical treatment technology, efficient separation and purification technology, air-water separation technology, self-sensing water flow regulation technology, water supply safety protection technology, and water volume monitoring technology. It utilizes light energy to stimulate catalytic reactions, exciting electrons on the surface of the photocatalyst under illumination, causing them to transition from the valence band to the conduction band, generating highly reactive free electrons and positive holes. These free electrons and positive holes can participate in various chemical reactions, including oxidation, reduction, hydrolysis, and decomposition. The built-in high-speed microfilter effectively removes pollutants such as suspended solids, organic matter, colloids, odors, pigments, and heavy metal ions from the water, achieving holographic filtration, purification, deodorization, and sterilization of the inlet water. The device is also equipped with an air-water separation reactor and a self-sensing water flow regulation device, providing a one-stop permanent solution to the challenges of separating municipal water from non-potable water and preventing contamination of municipal water. The system can self-sense and adapt to changes in water flow demands while ensuring the safety of domestic water. Additionally, the device features a real-time online safety protection system and a water volume monitoring system, enabling the statistical analysis, tracking, and remote transmission of water volume and loss data. The photocatalytic reactor combines the operational characteristics, features, and safety requirements of smart water systems, forming a powerful and comprehensive solution. It has become the ideal choice for low-carbon and energy-efficient water system treatment.