Road networks’ auto selecting is important but difficult in auto generalization. All roads in the map have’t been regarded as whole in present selecting methods. So the characteristic of road networks can’t be kept. A series of experiments have been done that road networks have been auto selected by different methods using graph theory. The results have been analyzed and compared

and then a better method has been proposed for road selecting. Through these experiments

the effect is better and it fits the necessity of road networks auto generalization.