Abstract. In this article we present an approach based the type of curve for detecting tangent vertices. First, the geometric features is used to determinate the curve type of the sub-stroke after corners extraction. Second, approximated piecewise parametric curves are obtained and the analytic curvature is token as the extraction principle of tangent vertices between straight line and curves when the vector product and the discrete curvature are applied to find tangent vertices between curves. The expeirmental result shows that our approach achieves a better accuracy in finding tangent vertices.