Method for preparing flame-retardant polyester fibers

The invention discloses a method for preparing flame-retardant polyester fibers. The method is characterized by comprising the following steps of: treating polyester fibers by using an alkali deweighting treatment technology, and mixing a certain amount of nano-scale flame-retardant masterbatch in an alkali liquor, wherein pits and holes are formed on the surfaces and the interiors of the polyester fibers subjected to alkali deweighting treatment, and the nano-scale flame-retardant masterbatch mixed in the alkali liquor can be filled in the pits and holes; and washing off the alkali liquor, and performing several posttreatment procedures to obtain the flame-retardant polyester fibers with a flame-retardant function. The functionalization and hydrophilic treatment are integrated, and the method has the advantages of short process flow, simple operation, low cost and the like.