Steam power system optimization design under uncertainty provides schedule plans in the design stage to avoid a conservative design based on deterministic design. The characteristics of uncertainties and their influence on optimization objectives and constraints were analyzed in this work. Uncertain factors were divided into two types. Fluctuations of some variables were expressed by time

and fluctuations of the others were expressed by probabilities. The first type variables caused the design to be a multi-period problem. Fluctuation of the second type variables were compensated based on stochastic programming to deal with constraint violations. A mixed integer linear programming model (MILP) based on multi-cycle stochastic programming with recourse was formulated to obtain optimal system configuration and operating state. Schedule plans were addressed in the design stage to satisfy uncertain steam and power demand.