The invention discloses a method for modifying both an extrusion-grade PA66 material and PET prepared from waste polyester textiles through chemical depolymerization, purification and polymerization so as to prepare a novel extruded alloy material. The method comprises the following steps: subjecting waste polyester textiles to depolymerization, filtration, decolorization and purification with glycerin residues having been heated to 260-280 DEG C, then performing polymerization to form PET, adding a compatibilizer and other additives, then adding a certain proportion of an extrusion-grade PA66 material, carrying out uniform mixing and then performing extrusion and granulation to obtain the novel special PET-PA66 extruded alloy material.