The invention relates to the technical field of pharmaceutical preparations, and discloses an oxybutynin transdermal plaster and a preparation method thereof. The transdermal plaster includes a backing layer and a medicated ointment, and the medicated ointment includes the following raw materials in mass percentages: 3-5% of oxybutynin and / or its pharmaceutically acceptable salt, 10-5% of sodium polyacrylate 15%, pre-cross-linked pectin 5‑8%, hypromellose 1‑2%, aluminum glycylate 0.5‑1%, pectinase@ethylcellulose / chitosan microcapsules 1.5‑3.5%, 10-15% of sorbitol, 1-2% of azone lauryl, 10-15% of ethanol, and the balance is water; the pH of the medicated ointment is controlled at 5.0-6.0 by a pH regulator. The oxybutynin transdermal plaster of the present invention has higher air permeability, and can promote the release of oxybutynin by slowly releasing pectinase in the later stage of application, thereby prolonging the duration and duration of the drug effect of the plaster. Application time.