复杂时段耦合型约束是制约大规模水电短期优化调度高效求解的主要因素之一。提出了一种水电站群变尺度优化调度方法，旨在通过增大时段步长，以弱化甚至消除时段耦合型约束，进而提高算法搜索效率，改善优化调度质量。在求解过程中，首先将原问题转换为多个具有相同调度周期、相同目标和控制需求但不同步长的水电站群优化调度问题，并按照步长从大到小的顺序依次求解各问题，面临问题的初始解由前一阶段大步长问题的优化出力结果确定，直至完成最小步长问题即原问题的优化求解。所提方法通过云南电网水电站群仿真调度实例得到验证，与单一尺度优化方法相比，结果质量和计算效率均得到不同程度地改善。“,”The complicated temporal coupling constraints greatly restrict the solving of large-scale short-term hydro scheduling problems. A mutative scale optimization method was developed to efficiently treat these constraints. The method enlarged the time step of the original problem for weakening even eliminating the temporal coupling constraints. Its final purpose was to enhance the convergence speed of solution algorithm and improve the poor solutions of the problem. During the solution process, a series of optimization problems with same operational horizon, objective and demands but different longer time steps were first generated according to the original problem, and then solved in descending order of time step. The initial solution for each problem depended on the optimized power generation of last problem with longer time step. The whole process will not terminate until the original problem with the shortest time step was addressed. The optimization of hydropower system operation in Yunnan Power Grid was used to test the mutative scale method. The simulation operation results show that the proposed method is capable of producing better solutions and cost less time than conventional single-scale optimization method.