This article first analyzes the strategic trend of energy development in the world, and the current situation, problems and challenges of energy in China. Then it proposes the guiding thought and principles for China's mid-long term development strategy of energy, emphasizing that a new energy strategy with Chinese characteristics must incorporate the Scientific Outlook on Development and it will secure the rational demand by scientific supply. The article defines the strategic position of different development stages of China's energy in the first half of the 21st century, and sets forth the basic content of "China's scientific, green and low carbon energy strategy"  and its 6 sub-strategies. The sub-strategies include: a.to strengthen the strategy of "saving first with control of the total" , introducing a concept of "ceiling"  for the consumption of coal and oil; b.to explore coal in a scientific way and to use it in clean and high efficient way and to adjust its position in China's energy strategy, introducing the concepts of "Scientific Producing Capacity of Coal"  and "Degree of Clean Use of Coal" ; c.to secure the strategic pillar position of oil and natural gas, taking natural gas as one of the key points in adjusting the energy composition; d.to actively develop hydro power and non-hydro renewable energy, developing them into one of the green pillars to China's energy; e.to actively develop nuclear energy taking it as a strategic choice for the sustainable development of China's energy; f.to develop highly efficient, safe, and smart grid system adoptable to multi-power sources characterized in China, and to develop off-grid power using and energy-storage technologies. "China's scientific, green and low carbon energy strategy"  is an economy and environment "win-win"  strategy, constituting an important part in the national strategy addressing the climate change. As the implementation of "China's scientific, green and low carbon energy strategy"  requires strong support of science and technology, the article proposes 3 levels of support by science and technology. It also gives the perspective of the development of energy in China in the first half of 21st century. Finally, it proposes several critical suggestions to the implementation of the above strategy.