Since power system energy-saving and emission-reducing plays a significant and practical role in sustainable development for human society, the research overview of power system power-purchasing plan is presented from the perspective of energy-saving and emission-reducing. First of all, this paper indicates the research background and significance of power system energy-saving and emission-reducing; then, the processing manners are summarized for energy-saving and emission-reducing according to power dispatch plan and electricity market respectively. The overview of optimization methods for solving power dispatch plan and power-purchasing plan in electricity market are stated and analyzed, and these key problems are pointed out as well. Finally, those important research directions that need to break through are concluded and refined, while providing the reference for this area of research in depth.