This paper has proposed a multi-scenario model of hydro-thermal optimal operation. On the premise of reliable supply of power and energy assurance, the objective of minimizing energy consumption is designed. Hydro-thermal optimal scheduling is formulated by the optimization of generation, maintenance plans and the water level. According to different scenarios of runoff, scenario tree model is established, while ensuring that optimization variables of all the forecast scenarios can satisfy the various constraints. For the complexity of the established model, based on integer algebraic model techniques, auxiliary state variables and associated constraints are introduced, and then the model is converted to a linear mixed integer programming problem. With the help of advanced GAMS model software, simulation system is established. Finally, using CPLEX solver, the scheme of hydro-thermal plants optimal operation is formatted. By the test and analysis of the practical examples including 2 thermal power units, 6 hydropower units, 17 maintenance programs, results demonstrate the rationality of the model and the availability of the method.