Firstly, energy saving is defined as the difference between actual energy intensity and anticipated energy intensity. And a model for measuring and appraisal of energy saving is established by using Taylor series in the paper. Secondly, analysis shows that if anticipated energy intensity is given, energy saving should be influenced mainly by two factors-the growth rate of energy consumption and production. The model can be used to calculate energy saving and to estimate its state. Finally, an empirical analysis of electricity saving of JiangSu province during 1995-2006 is provided to prove the model to be effective.