Abstract: The in house economic operation of hydropower plant is a kind of nonlinear constraint optimizing problem involving in continuous objective function and discrete variables. To overcome the difficulty in solving this optimization problem, the model is converted to optimizing problem with discrete variables and bound constraints, and a novel method combined penalty methods and Fast Electromagnetism Like Mechanism (ELM) was presented to solve it. The improved process of ELM, processing of discrete variables and the basic solving step were discussed in detail. The rapidity and feasibility of ELM is verified by simulation results of two examples and its comparing with that of genetic algorithm, which shows that its application has a good future in in house economic operation of hydropower plant.