A digital watermarking technique used as a protection and certifying mechanism of copyrighted creations including music, still images, and videos in terms of lading any loss in data, reproduction and pursuit. This study suggests using a selected geometric invariant point through the whole processing procedure based on the invariant point so that it will be robust in a geometric transformation attack. The introduced algorithm here is based on a watershed splitting method in order to make medical images strong against RST transformation and other processing. This algorithm also proved that is has robustness against not only RST attack, but also JPEG compression attack and filtering attack.