Abstract: With the SBM-Tobit two-stage model， an analysis is given on energy efficiency of different provinces and cities in China. The SBM model considering undesirable outputs is first used to evaluate the energy efficiency of Chinese provinces and cities from 1995 to 2010， whose results show that Shanghai， Guangdong， Hainan and Qinghai have the highest energy efficiency while Guizhou ranks the lowest. The panel Tobit model is then adopted to give a regression analysis， whose results indicate that the factors influencing energy efficiency include optimizing industrial structure， improving energy structure， reinforcing technological introduction and enhancing government influence. It is still difficult to explain the impact of internal technical innovation and market level on energy efficiency， and the effect of social and economic development on energy efficiency is changing from negative to positive.

Key words: energy structure, energy efficiency, SBM model, Tobit model