This paper presents a new Geometric Active Contour (GAC) model based on Lennard-Jones (L-J) force field, which is inspired by the theory of intermolecular interaction. It is different from gradient based GAC models in that the proposed model does not rely on any pre-computed edge map and is directly computed from image data. Moreover, it can integrate various information including grayscale, color and texture etc. The proposed L-J force field has two different characteristics controlled by a switch parameter c. In the case of c = 0, the force vector flows will bi-directionally converge to boundaries, and it will obtain a morphological dilation-like effect with c ≠ 0. We test the proposed method on various images, and the experimental results are very promising.