A cylindrical filter is a rainwater treatment device that utilizes the physical and chemical actions of the filtering medium to remove pollutants from rainwater. The filtering medium is custom-designed based on the nature of pollutants in rainwater, effectively targeting particles, organic matter, heavy metals, nitrogen, phosphorus, and other contaminants. The structure of the cylindrical filter is simple, installation is convenient, and maintenance is easy. It is widely used in various urban rainwater treatment applications, where the treated rainwater can either infiltrate into the ground, be discharged into natural water bodies, or be recycled for reuse.