Abstract: Leaf was important visual characteristic of plant. The leaf image extraction was a key step of modeling plant organs and living plant recognition, and had important value in the fields of automatic identification of plant and modeling. An efficient leaf image extraction method was proposed by combining active contours with cellular neural networks (CNN) in this paper. The active contours based on CNN provided a high flexibility and control for the contour dynamics. This approach had the advantage of applying a priori knowledge, put similar characteristics from both the implicit and parametric models, to improve the precise and robustness of image extraction. The results showed that the calculation method could be used for effectively extracting leaf vein and an ideal test results was obtained.