Abstract: We can make our web pages more vivid and representational by adding high quality animations into them.Some applications in the Internet,such as teleteaching,also need more animations to make them competitive.But the animations made with the old animation systems usually contain so much data that no one could stand the long time spent in transmitting them in the Internet.So most new animation systems today use vector images.In order to have animations more easy to make and get higher efficiency,we present a method of vectorizing the monochrome image automatically and explore its algorithm.