Research conclusions:(1) The highway traffic efficiency of Changsha － Zhuzhou-Xiangtan is in the normal level at present．(2) The difference of highway traffic efficiency between Changsha -Zhuzhou-Xiangtan and Yangtze River Delta，Pearl River Delta are mainly in aspects of highway network route length，per acre highway network density，unit length highway network output，real GDP per acre，passenger and freight volume etc． The highway traffic efficiency of Changsha-Zhuzhou-Xiangtan has some certain and potential advantages in the aspects of industrial enterprises above designated size comprehensive benefits ( economic index) and unit length highway network output ( highway network index) etc．(3) The main reason which leads to the difference between Changsha-Zhuzhou-Xiangtan and YangtzeRiver Delta，Pearl River Delta has been analyzed by applying the extension theory evaluation model which could calculate and evaluate the highway traffic efficiency objectively． This paper also provides the valuable reference to evaluate the highway traffic efficiency of other urban agglomerations of the country．