A method for preparing a transdermal absorption composition includes mixing rotigotine and an antioxidant at a weight ratio of 1:0.0001 to 0.1. A transdermal therapeutic system includes a substrate and a drug-containing adhesive layer disposed on the substrate and including an antioxidant at a weight ratio of 1:0.0001 to 0.1. The method and system of the present invention suppress the crystallization of rotigotine as well as the generation of related substances, thereby increasing the long-term storage stability of a therapeutic product containing rotigotine or related substances.
