Abstract: Energy saving and emission reduction is not only a breakthrough in the national long-term development plan,but also the transformation of enterprise's economic growth.As the key industry of national energy saving and emission reduction,some success have achieved in coal industry,but lack of power is commonly existed.The paper,firstly,based on economics perspective,analyzes the reasons of lack of power from enterprise,market and government levels,by means of microeconomics,economics of information and game theory methods.Secondly,it analyzes how policy solves the problem of lack of power from the three levels,and describes,as external power,how policy provides external driving force to energy saving and emission reduction.Furtherly,it illustrates it is essential for the existence of policy and will be theoretical basis of further policy making.