The invention discloses a method for preparing a silver-containing PET based composite resin material. In the method, a monomer of terephthalic acid (PTA) or dimethyl terephthalate (DMT) for synthesizing PET and a precursor silver glycol colloid solution are polymerized in situ to prepare the material. The PET/Ag composite resin material prepared by the method has high spinnability and antibacterial property, and the preparation method has smart concept, simple process, short preparation period and low production cost without pollution, and is suitable for large-scale industrial production.