The present invention relates to a method for preparing a composite resin composition by regenerating secondary battery waste separators of which one surface or both surfaces are coated with ceramic particles or aramids, and, more specifically, to a method for preparing a composite resin composition through: i) a pretreatment step of crushing secondary battery waste separators coated with ceramic particles and compression-crushing same into a smaller volume; ii) a step of mixing the pretreated waste separator material with a polyolefin-based material having excellent fluidity, other modifiers and additives, and melting, uniformly kneading and extruding same; and iii) a step of processing same into a pellet form. The present invention relates to an economical, efficient and eco-friendly process capable of preparing a variously usable novel composite resin composition from separator scraps coated with ceramic particles or aramids, which are generated during the manufacture of secondary batteries, and separators, which are inferior goods requiring disposal.