The invention discloses a method for prolonging a switching period of a functional polyester production device prepolymer filter. The method is mainly and technically characterized in that a parallel multiloop filter design scheme is adopted, wherein each loop is formed by connecting a discharge pump with a plurality of groups of prefilters in series, and each group of prefilters comprises two prefilters (wherein one is normally used, and the other one is used for later use) which are connected in parallel. The switching period of the prepolymer filter is greatly prolonged; the labor intensity and labor cost of the switching filter are lowered, so that the related personnel have enough time to install a cleaned prepolymer filter cartridge; and moreover, the production cost of a functional polyester melt is greatly reduced.