Efficient scale inhibitor and dispersant, especially suitable for reverse osmosis system with high content of barium and strontium in feed water and serious scale tendency of barium sulfate and strontium sulfate. It can effectively prevent fouling in a wide concentration range of fouling substances. The use of QD-486 in reverse osmosis system (RO), nanofiltration system (NF), ultrafiltration system (UF) can greatly reduce equipment investment and operating costs, and can replace the ion exchange process to ensure that it is still under high feed water concentration conditions The ideal reverse osmosis pretreatment process can run normally.