The skeleton is an important feature in the representation of a shape in mage analysis. This paper has two parts. First, we propose a fast, efficient and accurate skeleton extraction method based on the criterion which can be used to determine whether a given pixel is a skeleton point independently. Second, since the skeleton algorithm is sensitive to an object’s boundary noise, we propose a pruning method based on bisector angle, which can completely remove redundant protrusions and obtain accurate skeleton and preserve the original topological property of a shape.