Smog is a severe pollution problem in the developing city. The environmental pollution is the direct reason for the smog; it is caused by the excessive development. At the present, the global market are extend led high bay for its environmental friendly and many governments provide subsidies for retrofitting with led high bay . Let us go into the details of the energy savings of the led high bay. The led high bay saves more than half energy than the energy lamp s. What more incredible is that the led high bay only consume 10 percent energy compared to the candescent lamp. For an example, 1500W conventional high pressure lamps will cost 200 dollars per year, after retrofitting with the led high bay, the led high bay could save 150 dollars per year with the 450W led high bay.