Optimal operation of cascade hydropower plants can make full use of water resources and maximize the benefit of power generation, energy-saving benefit between hydro and thermal power, and social benefit of flood-drought control. Therefore, this paper proposes a scheduling strategy for cascade hydropower plants considering the coordination of a variety of factors, taking into accounts both the economic and social benefit. The spill water is decomposed into three parts: power generation spill, flood control spill and anti-drought spill. The concept of virtual power plant is introduced to represent the site of flood control spill, and its mathematic expression is put forward. The comprehensive benefits of hydro and thermal power is considered, including the coordination of water scheduling, power output and energy cost and pollution emission of thermal plants, the coordination of power outputs of hydro plants, water flow of electric generation, power generation spill, flood control spill, anti-drought spill and other water power parameters. So an energy saving scheduling model is proposed with multi-objects of minimum water spill, minimum energy cost and pollution emission of thermal plants. Finally, the proposed method is simulated on a system consisted of 4 cascade hydro power plants and 3 thermal power plants for three cases: normal, flood control and anti-drought. The results verified the feasibility of the proposed method with its energy saving and social benefit.