Security filters are mainly used for production water filtration, alcohol filtration, pharmaceutical filtration, acid-base filtration, and reverse osmosis RO membrane front security filtration in industries such as drinking water, domestic water, electronics, printing and dyeing, textile, and environmental protection. They have high flux, low material cost, polished or matte appearance, and acid pickling and passivation treatment on the inner surface. The main function is to protect the water treatment system and ensure the effluent quality standards. This article mainly introduces the principle and characteristics of security filters.