The energy function of the classical active contour model is composed of the internal energy and the external energy

the internal energy is used to restrict the Snake shaping and the external energy leads the convergence process of active contour. Actually

the convergence accuracy of the objective contour is mainly determined by the external energy

while the internal energy is only to ensure that the contour shapes with reason. Because the internal energy includes a few unrelated factors

it has some side-effect on the convergence accuracy of the objective contour. So in this paper a new active contour structure is presented to solve the problem

in which the internal energy is separated from energy function

only the external energy is applied to the convergence process of active contour

at the same time the image energy and the control energy are redefined

a revised contour function is introduced

the continuity and smoothness is embodied in the Snake shaping process. Experimental results show that the active contour algorithm under new structure is little dependent on the initial contour and can converge quickly; the number of control points adaptively changes also can increase the tracking accuracy of objective contour.