Abstract: Geometrical Active Contour（GAC） models，i.e.，active contour models implemented via level set methods，have recently become very popular image segmentation methods in image processing and computer vision.Almost these models rely on the Halting Speed Function（HSF），which is typically the function of the image gradient，to stop the active contour（evolving curve）on the boundary of the desired object.In order to speed up the evolution of the active contour，this paper proposes a scheme that the scale transform is applied to the HSF.Experimental results on four synthetic and real world images show that the proposed scheme can significantly reduce segmentation time and perform better in the presence of concave and weak object boundaries.