Energy efficiency causes long-term energy rebound effect. Based on this mechanism and assumed the energy efficiency to be endogenous, the expression of energy saving and energy rebound effect is gotten from a distribution equation. This equation includes energy efficiency, economic income, capital and energy consumption. In addition, sensitivity analysis of this expression is made. The result shows that: (1) The reverse effect is always existed in the long-time energy efficiency in China. To a large extent, the economic growth in China relies on capital and energy input, so that the increase of energy efficiency causes the increase of energy intensity effect under the action of the capital investment; (2) Reducing the capital intensity effect and energy-capital substitutional effect will be helpful to bring down the energy intensity effect; (3) Reducing production dependence on capital and energy will reduce the energy rebound effect; (4) Increasing the elasticity to the labor given by economic income and the elasticity to energy efficiency given by energy usage will reduce the energy rebound effect.