Abstract: The contour features of a leaf mainly include the aspect ratio, area, boundary curvature, and slope, which are very important to classify and recognize the tree. The mathematical morphology combined with pixel tracking algorithm is used to separate petiole of the leaves. Using the Hotelling transform, the minimum enclosing rectangles and the aspect ratios of leaves are obtained. Based on the finite-difference algorithm, the boundary slopes and curvatures of the key parts of the different leaves are also obtained.