In the paper a method for curve evolution based on image gravitation andM2S model is presented. A two -stage algorithm is thus proposed: image gravitation is first proposed to find the optima of reference points, reference points rapidly converge near image edge; The method based on narrow band level set is presented to solve the research of accurate contour. The active contourmodel’s sensitivity to its initial position, the poor convergence to boundary concavitieswhich exists in the traditional Snake and sensitivity to noise are solved. In each step ofM2S iteration, the paper only dealswith the data in a narrow band instead of the whole image, so the computational complexity is decreased.